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JOURNAL OF APPLIED ECONOMETRICS J. Appl. Econ. 26: 549– 579 (2011) Published online 14 December 2009 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/jae.1134 HOW DOES HETEROGENEITY SHAPE THE SOCIOECONOMIC GRADIENT IN HEALTH SATISFACTION? ANDREW M. JONESa AND STEFANIE SCHURERb * a b Department of Economics and Related Studies, University of York, York, UK Melbourne Institute of Applied Economic and Social Research, University of Melbourne, Parkville, Victoria, Australia SUMMARY Individual heterogeneity plays a key role in explaining variation in self-reported health and its socioeconomic gradient. It is hypothesised that the influence of this heterogeneity varies over levels of health and increases over the life cycle. These hypotheses are tested by applying a threshold-specific alternative to the conditional fixed-effects logit and longitudinal data from Germany. Our results suggest that income influences health at the lower end, but not at the higher end of the health distribution, once unobservable factors are controlled for. The underlying assumptions of the statistical model matter for this conclusion, in particular for the older age groups. Copyright 2009 John Wiley & Sons, Ltd. Received 8 October 2007; Revised 19 February 2009 1. INTRODUCTION We use data of the German Socio-Economic Panel (GSOEP) to explore the socioeconomic gradient in self-reported health satisfaction. The main focus is on the appropriate choice of an econometric specification that accommodates omitted variable bias, nonlinearities in the income effect, and changes in heterogeneity over the life cycle. Three hypotheses are tested: (1) whether the choice of the statistical model, and its underlying assumptions on the relationship between unobserved factors and income, matters for the conclusions on the effect of income on health; (2) whether there are nonlinearities in the effect of income on health, i.e. a stronger effect of income on individuals in lower health states than on individuals in higher health states; and (3) whether the influence of unobserved heterogeneity on both income and health increases over the life cycle and, therefore, whether the potential bias due to omitted variables increases for older age groups. A controversial question in economic policy is whether it makes sense to redistribute income to improve population health (Deaton, 2002). The question is strongly disputed, because the direction of the causal link may run both ways: from childhood health to socioeconomic status (Almond, 2006; Bleakley, 2007; Currie and Stabile, 2006; Behrman and Rosenzweig, 2004; Black et al., 2007), but also from low socioeconomic status to health (Grossman, 1972; Frijters et al., 2005a; Duflo, 2000; Lindahl, 2005; Lleras-Muney, 2005). Judgements about the health–income nexus are further complicated by methodological limitations induced by the data available for assessing the link. Usually, health outcomes are approximated by subjective, i.e. self-assessed, health measures. Even though self-assessed health has Ł Correspondence to: Stefanie Schurer, Melbourne Institute of Applied Economic and Social Research, The University of Melbourne, 161 Barry St, Alan Gilbert Building Level 7, Melbourne 3010, VIC, Australia. E-mail: [email protected] Copyright 2009 John Wiley & Sons, Ltd. 550 A. M. JONES AND S. SCHURER been widely accepted as a reliable predictor of morbidity and mortality (Mossey and Shapiro, 1982; Idler and Benyamini, 1997; Mackenbach et al., 2002), the measure is strongly influenced by individual-specific, and usually unobserved, heterogeneity. On the one hand, individuals with the same level of objective health may perceive, and thus report, their health differently (Juerges, 2007; Lindeboom and Van Doorslaer, 2004; Maurer et al., 2007). On the other hand, health status, no matter whether it is measured objectively or subjectively, is largely driven by genetic factors or personality traits, which are also highly correlated with socioeconomic status. For instance, Auld and Sidhu (2005) show that both schooling and cognitive ability are strongly associated with lower health status and that intelligence accounts for about one quarter of the association between schooling and health. Singh-Manoux et al. (2005) conclude that up to 40% of the relationship between socioeconomic status and self-rated health can be explained by cognitive ability. Children’s IQ strongly predicts adult socioeconomic outcomes (Jencks et al., 1972, 1979) and 20–40% of total observed variation in education, occupation, and earnings can be linked to genetic differences in cognitive ability (Gottfredson, 2004). There is also evidence that IQ is generally a very good predictor of health outcomes (Gottfredson, 1997, 2002; Gottfredson and Deary, 2004) and, specifically, children’s IQ predicts survival rates in older age (Whalley and Deary, 2001; Betty and Deary, 2004). The problem of confounding and the necessity to control for cognitive ability has been widely acknowledged in the labour economics literature (Blackburn and Neumark, 1995; Card, 1995). The strong influence of individual-specific and unobserved factors is also widely debated in the happiness literature (Lykken and Tellegen, 1996), which render the identification of a causal effect of important micro- and macroeconomic variables on life satisfaction difficult (see Clark et al., 2008, for an overview of the literature). Reporting and omitted variable bias suggests the use of panel data methods that allow for a correlation between unobserved heterogeneity and the regressors of the model. In general, these are not readily available for nonlinear models, such as binary and ordered-choice models, due to the incidental parameter problem (Neyman and Scott, 1948). The conditional fixed effects logit (Chamberlain, 1980) provides consistent parameter estimates, but it incurs a great loss of information, a reduction in sample size, and marginal effects cannot be easily calculated due to the lack of information on the distribution of the individual heterogeneity (Wooldridge, 2002). A recent extension of Chamberlain’s model, the conditional ordered fixed effects logit (Ferrer-i-Carbonell and Frijters, 2004; Frijters et al., 2004a,b, 2005a), suggests a method to reduce the drastic loss in the number of observations. Its original formulation, however, is highly computation-intensive and it cannot identify changes in health and well-being across the full distribution. Other approaches relax the orthogonality assumption to apply pooled ordered, generalised ordered (Terza, 1985) or random effects ordered models and their extensions based on the ‘correlated effects’ approach of Mundlak (1978) and Chamberlain (1980). Generalised ordered probit models relax the single index assumption to control for reporting bias and have been widely applied in the literature (Kerkhofs and Lindeboom, 1995; Groot, 2000; Sadana et al., 2000; Shmueli, 2002; Van Doorslaer and Jones, 2003; Hernandez-Quevedo et al., 2008; Contoyannis et al., 2004; Etilé and Milcent, 2006; Jones et al., 2006; Gannon, 2005; Pudney and Shields, 2000; Boes and Winkelmann, 2006). Despite their wide application, the threshold-specific parameter estimates obtained from generalised ordered response models are theoretically not identified, without making additional assumptions about parameter values to ensure that the thresholds are ordered consistently (Cunha et al., Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae HETEROGENEITY AND HEALTH SATISFACTION 551 2007; Ronning, 1990). In addition, parameter estimates may be biased due to the presence of confounding factors as discussed above. The magnitude of the bias is a matter of empirical evidence, but it is likely that it is larger for older age groups, assuming that the influence of unobservable factors on both health and socioeconomic outcomes increases over the life cycle. There are convincing arguments for this assumption. Health status naturally worsens over the life cycle due to idiosyncratically accumulated health shocks, either due to accidents or genetic factors (Liang et al., 2005; Frijters et al., 2005b). Scarr and McCartney (1983) argue that genetic factors become more influential in determining choices, e.g. those determining socioeconomic status (tertiary schooling, professional training, on-the-job training) and health behaviours (diet, smoking, exercise) in older age. This has to do with the fact that, once they leave the nurturing environment of the family and compulsory schooling, individuals engage in niche-building activities that correlate with their talents, interests, and personality characteristics. It has also been shown that the influence of genetic factors on variations in cognitive ability increases over the life cycle (McGue et al., 1993; Plomin, 1986; Plomin and Petrill, 1997; Bouchard, 1998). In light of these theoretical and statistical caveats, we take a pragmatic approach to identifying the effect of income on health. We rely on a large sample drawn from the GSOEP, and proxy health status with an ordered categorical measure of health satisfaction. For each possible threshold value, for which health satisfaction can be dichotomised, we estimate a conditional fixed-effects logit model. This formulation allows for nonlinearities in the effect of income on the underlying health status. Whether or not nonlinearities are present is then tested by comparing the estimated coefficients against those obtained from the conditional ordered fixed effects logit (Ferrer-iCarbonell and Frijters, 2004). Whether or not the underlying assumptions of the econometric model matter for assessing the link between income and health is tested by comparing the marginal effects against those obtained from pooled ordered and random-effects logits. Finally, whether the omitted variable bias increases over the life cycle is tested by interacting the effect of income on health with age-group dummy variables. The results reveal that income influences health at the lower end of the health distribution, but not at the higher end, once unobservable factors are controlled for. The underlying assumptions of the statistical model matter for this conclusion. The income gradient for older age groups is more sensitive to omitted variable bias than the income gradient for younger ones. The remainder of the paper is structured as follows. Section 2 outlines the econometric models, discusses their underlying assumptions and explains the methods to calculate marginal effects. Section 3 describes the data. Section 4 presents the estimation results and the tests for heterogeneity in the age-specific income coefficients, the differences in the marginal effects of income across model assumptions, and the robustness of the marginal effects with respect to their calculation method. Section 5 discusses the implications of the results. 2. ECONOMETRIC METHODOLOGY 2.1. Model We specify a reduced-form model for latent health HSŁit , which is the outcome of health-related choices and individual circumstances: HSŁit D ˛i C ˇ0 Xit C uit Copyright 2009 John Wiley & Sons, Ltd. 1 J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 552 A. M. JONES AND S. SCHURER where i D 1, . . . , N and t D 1, . . . , Ti (unbalanced panel). ˛i is an intercept term that varies across individuals and represents in this context cognitive ability, Xit is a vector of exogenous variables that influence health, and uit is an idiosyncratic error term, assumed to be distributed as standard 2 logistic uit ¾ 0, 3 . is a monotonically increasing function of the linear index. Reported health status HSit D j for j 2 f1, . . . , Jg is observed if latent health lies within an interval between ij1 and ij : HSit D j if ij1 < HSŁit ij 2 We allow the individual thresholds to differ across individual-specific, but time-invariant characteristics: 3 ij D ij1 C Qij where the Qij are individual- and threshold-specific effects and where Qij > 0 8 i.1 The individualspecific threshold values are interpreted as differences in reporting behaviour that are a function of personality characteristics that influence the perception and assessment of health (e.g. optimism). These individual effects are assumed to be increasing in categories, which ensures that ij1 < ij 8 i, j 4 Condition (4) states that our specification respects stochastic monotonicity and is coherent with the ordering of the categorical outcomes (Cunha et al., 2007, pp. 1290–1291). In contrast to our formulation, generalised ordered-response models (Terza, 1985; Maddala, 1983), which allow the thresholds to be a function of observable time-varying characteristics, do not guarantee that each individual has a coherent ordering of thresholds. Cunha et al. (2007) and Ronning (1990) have demonstrated that threshold-specific parameter estimates are not identified without making additional assumptions about parameter values to ensure that the thresholds are ordered consistently.2 Plugging equation (3) into equation (2) and replacing HSŁit by the linear index of equation (1), then HSit D j if ij1 < ˛i C ˇ0 Xit C uit ij 5 By rearrangement, we obtain ij1 ˛i C ˇ0 Xit < uit ij ˛i C ˇ0 Xit 0 0 6 ˛i ij1 ˇ Xit < uit ˛i ij ˇ Xit 7 ˛ij1 ˇ0 Xit < uit ˛ij ˇ0 Xit 8 Equation (8) results naturally by rearranging, using equation (3) and defining ˛ij D ˛i ij . The latter makes clear that we cannot separately identify the individual-specific threshold ij , 1 As an example, assume Qij D exp˛ij . the generalised model is estimated by FIML failure of the identification restrictions will manifest itself as failure to compute the log-likelihood, as contributions to the log-likelihood involve the log of a negative number (see equation (10)). In practice, the generalised model is often estimated as separate binary-choice models, in which case the estimated parameters may not satisfy the coherency conditions. 2 When Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae HETEROGENEITY AND HEALTH SATISFACTION 553 which is a function of personality traits affecting perception, Qij , from ˛i , which we assumed to be cognitive ability. The probability that an individual reports health status HSit D j is Pitj D PHSit D jj˛ij , Xit D F˛ij ˇ0 Xit F˛ij1 ˇ0 Xit 9 where F D . is the logistic distribution function. The sample log-likelihood function to be maximised is ln Lˇ D Ti N J ditj ln[˛ij ˇ0 Xit ˛ij1 ˇ0 Xit ] 10 iD1 tD1 jD1 Equation (10) presents a generalisation of ordered response models with individual effects Qij in the cut-points , but which differ by time-invariant factors only. Each individual shares the same ordering of health states, i.e. very bad < bad < fair < good < very good, but for each individual the position of each threshold varies by a person-specific factor Qij . For instance, for optimists, the threshold may systematically shift to the left, i.e. for a given level of the latent health index they will tend to report a better level of health satisfaction than less optimistic individuals. In practice, we estimate this model with a conditional fixed-effects logit (Chamberlain, 1980) for each of the J 1 threshold values into which the ordered categorical dependent variable of health satisfaction can be dichotomised. In doing so, we condition out the threshold-specific individual unobserved heterogeneity (˛ij ). Applying Chamberlain’s (1980) approach to all possible threshold values yields heterogeneous parameter vectors for our variables of interest. Evidence of variation in the coefficients over the categories may be interpreted as evidence of nonlinearity in the latent health index that is not captured by including logarithmic or polynomial transformation of the regressors X within the linear index. For instance, with concavity of . in the latent health index, variables such as income may play a greater role at the bottom of the health distribution than at the top.3 We test for the presence of nonlinearities by comparing our results with those obtained from the conditional ordered fixed-effects logit (Ferrer-i-Carbonell and Frijters, 2004). The latter assumes homogeneous coefficients across categories and threshold-independent unobserved heterogeneity (ˇj D ˇ) and (˛ij D ˛i ). For estimation of the conditional fixed-effects approach each dependent variable is recoded to B,j equal 1 (HSit D 1) if health satisfaction remains below or equal to the threshold j: B,j HSit D 1 if HSit j B,j HSit D 0 if HSit > j where j 2 f1, . . . , J 1g and B stands for binary variable. To eliminate the individual fixed effect from the log-likelihood function, this method takes advantage of a set of sufficient statistics. We have to find J 1 sufficient statistics j for ˛ij , for which the distribution of the sample, given j , does not depend on ˛ij : B,j B,j fHSit jXit , ˛ij , j D fHSit jXit , j 3 Our 11 estimation approximates the nonlinearity of . by a step function, with steps at the boundaries of the categories. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 554 A. M. JONES AND S. SCHURER i B,j In the case of the logistic regression, Andersen (1970, 1971) shows that TtD1 HSit is a sufficient statistic for ˛ij and that conditional ML estimates are consistent. We use this result for the J 1 Ti Ti B,j binary equations. Conditioning on tD1 HSit D tD1 ditj , i D 1, . . . , Nj , and t D 1, . . . , Ti , B,j where ditj D 1 if HSit D 1 and 0 otherwise, the log-likelihood is in our case ln L D J1 ln Lj IHSi1 > j, . . . , IHSiTi > jj jD1 Nj J1 jD1 iD1 exp ln Ti B,j HSit X0it exp d2Bij T i IHSit > j D cj D tD1 ˇj tD1 Ti 12 ditj X0it ˇj tD1 where Bij D dj D di1j , . . . , diTi j jditj 2 f0, 1g and Ti tD1 ditj D Ti D B,j HSit D cj . tD1 Bij is the set of all possible sequences of 0s and 1s for which the sum of Ti binary outcomes i i B,j equals TtD1 ditj D cj . Those individuals for whom 0 < TtD1 HSit < Ti does not hold true do not contribute to the log-likelihood and, therefore, will be dropped from the sample. Hence sample sizes Nj across the J 1 categories will differ, i.e. NjD1 6D . . . 6D NjDJ1 . In total, there will be Ti 1 alternative sets Bij . This methods yields J 1 estimated coefficient vectors ˇj . In contrast, Ferrer-i-Carbonell and Frijters (2004) estimate the coefficient vector ˇ assuming linearity in the effect of income on true health. Their method collapses the ordered categorical variable into a binary format using an individual specific threshold ji , rather than one threshold j applied to the entire sample. To find this individual threshold, the authors maximise a weighted sum of J 1 log-likelihood functions, similar to Das and Van Soest (1999), subject to the constraint that the sum of squared weights across all possible threshold values across all individuals must be equal to the number of individuals in the sample. This constraint means that one can use only weights wij 2 f0, 1g, and so only one of J 1 log-likelihood functions for each individual contributes to the total log-likelihood, and all the others will drop out. This log-likelihood function is the one for which the analytical expected Hessian is minimised. B,j In practice, the authors dichotomise their dependent variable into HSit for each possible threshold value j. In a second step, Chamberlain’s estimator is used choosing one arbitrary threshold value that equally applies to all individuals: let us say j D 3. The predetermined B,j parameter vector Ǒ jD3 along with the realisations of HSit and Xitj for all j 2 1, . . . , J is used to calculate analytically for each individual, which surpasses the corresponding threshold j, the expected Hessian. In a third step, the log-likelihood function Lij for which the analytical expected Hessian is minimised receives the weight wij D 1 and the corresponding threshold value ji is earmarked. In a last and fourth step the parameter vector of interest is estimated with the Chamberlain approach, dichotomising the ordered variable according to the individual-specific threshold ji . As an approximation one can simply use the within-individual mean values of the Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae HETEROGENEITY AND HEALTH SATISFACTION 555 health status score as the threshold. Using the mean values as cut-off values one loses only those individuals who never change their health status over time.4 Our model could also be estimated with J 1 random effects logit specifications, but we have to assume that the threshold-specific unobserved heterogeneity ˛ij is independent of Xit . Whether this assumption is tenable depends on the context. As argued in the Introduction, there are good reasons to expect that unobserved factors influence strongly both socioeconomic status and health. Hence, imposing orthogonality most likely will yield inconsistent parameter estimates. Comparing, therefore, marginal effects from such a model with marginal effects from the conditional fixedeffects logit is a test for the potential cost of the inappropriate assumption of uncorrelated effects. A similar case holds for applying a pooled ordered logit model which, besides the orthogonality assumption, imposes ˇj D ˇ. 2.2. Test for Heterogeneity in Income Coefficients We test whether nonlinearities in the effect of income on health, which we understand as an additional form of heterogeneity, can be observed in the data. To do this we test the null hypothesis that the estimated coefficient vectors across four different models that result from equation (12) are not statistically different from each other. For the testing, we stack the four datasets and interact the regressors of the model with each of three dummy variables that take the value 1 if the observation belongs to sample j 1, and 0 otherwise. B,j dj D 1 if HSit D 1 if 0 < Ti 1 B HSitj < 1 Ti tD1 13 Then we re-estimate a conditional fixed effect logit model of any change in health satisfaction (over one particular threshold value j) on the set of interacted regressors for the stacked sample: 0 0 0 0 HSBŁ it D ˛i C ˇ Xit , ˇ2 d2 Xit , ˇ3 d3 Xit , ˇ4 d4 Xit C uit 14 The null hypothesis is that the coefficient vectors on the interaction terms ˇ2 , ˇ3 , and ˇ4 equal zero: 15 H 0 : ˇ2 D ˇ 3 D ˇ 4 D 0 For the case the null hypothesis cannot be rejected, we conclude that using a conditional ordered fixed-effects logit proposed by Ferrer-i-Carbonell and Frijters (2004) is sufficient to account for heterogeneity in the data. 2.3. Marginal Effects Marginal effects for the logarithm of net monthly household equivalent income are evaluated for each age-specific group at the mean value of the independent variables for each group. Computing 4 Many thanks to Paul Frijters for valuable comments, parts of the GAUSS syntax and making us aware of this simplification that can be implemented easily in STATA. We estimated our models by both the full computation method in GAUSS and its simplification in STATA. Since results are very similar, we conducted the entire analysis with the simplified approach. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 556 A. M. JONES AND S. SCHURER the marginal effect for the ordered logit is fairly standard (Cameron and Trivedi, 2005, p. 522). For calculating the marginal effects for the conditional fixed and random effects logits we need to make an additional assumption on the distribution of the unobserved effect ˛ij . One common solution is to set its estimate ˛O ij D 0. In this case the marginal effect is calculated by the logit density function multiplied by the coefficient of interest: MEj D Ǒ j Xit Ǒ j C ˛O ij 1 Xit Ǒ j C ˛O ij D Ǒ j Xit Ǒ j 1 Xit Ǒ j 16 where j stands for the particular threshold value. Another solution is to find a valid approximation for ˛O ij . Analytically, the individual fixed effect is the mean difference between the latent health status and the linear index, evaluated at the mean value of all regressors. It can be approximated by B,j ˛O ij ' 1 HSi Xi Ǒ j 17 B,j where HSi is the sample average of the observed health status variable that results from dichotomising the ordinal variable at threshold j, Xi is the individual-specific sample average of each exogenous variable in the model, and 1 is the inverse of the logistic function. Ǒ j is obtained from a conditional fixed-effects logit estimated for threshold j. Since all individuals for B,j whom HSi D 0, 1 do not contribute to the log-likelihood, possible values for 1 . are strictly bounded. In light of the hypothesis that there should be an increasing variability in the individual fixed effect over the life span of an individual, we calculate the average of the individual fixed effect for each age group k: N 1 ˛O k D ˛O ij Dk 18 Nk iD1 where Dk is an indicator variable that takes the value 1 if the individual belongs to the particular age group k, and 0 otherwise. The total number of individuals in each age group is indicated by Nk , where N is the total sample. To make the marginal effects calculated from a random-effects logit comparable to those of a pooled ordered logit, we have to multiply the coefficients ˇ by 1 O (Arulampalam, 1999), O ˛2j where O D . 1 C O ˛2j 3. DATA We use 22 waves of the GSOEP running from 1984 to 2005.5 As a measure of self-reported health we use satisfaction with health, as it is available for all years of the sample. Satisfaction with health 5 The data used in this paper were extracted from the SOEP database provided by the DIW Berlin (http://www.diw.de/soep) using the add-on package PanelWhiz v1.0 (October 2006) for Stata. PanelWhiz was written by Dr John P. HaiskenDeNew ([email protected]). The PanelWhiz generated DO file to retrieve the SOEP data used here and any Panelwhiz plug-ins are available upon request. Any data or computational errors in this paper are our own. Haisken-DeNew and Hahn (2006) describe PanelWhiz in detail. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 557 HETEROGENEITY AND HEALTH SATISFACTION Density .25 0 0 .05 .1 .15 Density .1 .05 .15 .2 (b) .2 (a) .25 is coded from 0 to 10, where 0 means the lowest possible level of self-reported health and 10 means the highest possible level. This measure has been used in the literature to proxy the more commonly applied measure self-assessed health (e.g. Frijters et al., 2005a). This latter measure is coded from 1 to 5, where 1 represents bad self-reported health and 5 very good self-reported health. Figure 1 displays the distribution of satisfaction with health for both men and women in the sample. The two distributions are almost identical; they are both skewed to the left, and the most commonly reported values are 7 and 8. Figure 2 illustrates the distribution of self-assessed health for both men and women. Again, both distributions are similar for men and women, skewed to the left, and the most commonly reported values are 3 and 4 (satisfactory and good health). To make satisfaction with health (SWH) comparable to self-assessed health (SAH) and our results manageable, we collapse SWH into a five-point scale. The mapping is undertaken according to overlaps in the cumulative distribution functions, the cross-tabulations of each category and the 0 1 2 3 4 5 6 7 8 9 10 0 1 Satisfaction with health 2 3 4 5 6 7 8 9 10 Satisfaction with health Women Men (a) .1 .2 Density .2 0 0 .1 Density .3 .3 .4 (b) .4 Figure 1. Distribution of health measure: satisfaction with health (SWH) 1 2 3 4 5 1 2 3 Selfassessed health Selfassessed health Men Women 4 5 Figure 2. Distribution of health measure: self-assessed health (SAH) Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 558 A. M. JONES AND S. SCHURER correlation structure between each sub-category of the two measures. A detailed description of the recoding is provided upon request. We choose the following recoding: ž SWH ž SWH ž SWH ž SWH ž SWH D 0, D 3, D 5, D 7, D 9, 1, 2 into SAH D 1 (bad health) 4 into SAH D 2 (poor health) 6 into SAH D 3 (satisfactory health) 8 into SAH D 4 (good health) 10 into SAH D 5 (very good health) The main focus of this paper is the impact of socioeconomic status on health satisfaction and, in particular, the role of household income. Another proxy for socioeconomic status is education; however, this measure shows little variation over the years. The chosen econometric framework of conditional fixed-effects logits requires variables that vary over time. Equivalent income is constructed by dividing net monthly household income by the square root of the number of household members.6 We refrain from using relative income, which has been emphasised in the happiness literature. Recent evidence has shown that relative income has little effect on self-reported health (Jones and Wildman, 2008; Gravelle and Sutton, 2003, 2009; Lorgelly and Lindley, 2008; Miller and Paxson, 2006). Some of the arguments against relative income are that it may have a delayed effect of 15 years or more (Subramanian and Kawachi, 2004) and the difficulties in identifying the appropriate peer group. The income variable is interacted with six age-group dummy variables to obtain a vector of six different income coefficients. Age groups are defined from 16 to 30, 31 to 40, 41 to 50, 51 to 60, 61 to 70 and 71 and older. These age groups are also required to test the hypothesis that the omitted variable bias should become more prominent for older individuals. In addition, we control for the total number of years of schooling, immigrant and marital status, the number of household members, geographical location (East versus West Germany, and the Bundeslaender), employment status, working disabilities, the number of hours overworked during the week, and time effects. We separate our sample into men and women to account for the gender-specific difference in the relationship between socioeconomic status and health. In total, our sample contains 134,626 person-year observations for men and 145,030 person-year observations for women. Detailed summary statistics are provided in Table III, separately for men and women, in the Appendix. 4. ESTIMATION RESULTS 4.1. Interpretation of Coefficients The next two subsections show the estimation results for men and women for three different models. The models comprise the pooled ordered logit (POL), the random-effects logit (REL), and the conditional fixed-effects logit (CFEL) specifications. The latter two models both assume 6 This is a simplification applied in OECD studies to adjust household income for needs. It is an approximation of the OECD modified equivalence scale (Hagenaars et al., 1994), which assigns to the household head a value of 1, each additional member of the household a value of 0.5, and each child below the age of 16 a value of 0.3. We tested both methods. Since the results do not differ, we opted for the simplified version. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae HETEROGENEITY AND HEALTH SATISFACTION 559 the presence of threshold-specific time-invariant heterogeneity, but differ in their assumption on the relationship between this heterogeneity and the regressors of the model. The first column of Table IV in the Appendix report the estimated coefficients of the POL model for men and women, respectively (estimated coefficients for time dummy variables are omitted and will be provided upon request). The results suggest that East Germans are generally less likely to report a high level of health satisfaction, all age groups are less likely to report high levels of health satisfaction than the youngest group aged between 16 to 30, and that the diminishing probability is increasing with age. Extra household income is associated with higher levels of health satisfaction and this effect is also increasing with age. Whereas the number of years of education are associated with greater levels of health satisfaction, unemployment, work disabilities, and hours of overwork are associated with lower levels. Singles report on average higher levels of health satisfaction, an association which may be mainly driven by the age of singles. Last, individuals living in larger households are associated to report greater levels of health satisfaction. These results are similar for women and, overall, they reflect the trends in the empirical literature. The results on the estimated coefficients obtained from various random-effects logits specifications are reported in columns 2–7 of the same tables, whereas the estimated coefficients obtained from various conditional fixed effects logits are reported in Table V in the Appendix. 4.2. Tests for Heterogeneity in Coefficients Tables I and II show the p-values of the null hypothesis for each possible pairwise test of equality of the coefficients, obtained from different CFEL specifications for men and women, respectively. Coefficient and full results are reported in columns 1–6 in Table V in the Appendix.7 Overall, the test results suggest that the heterogeneity in the effect of income on health satisfaction is present especially for the middle-aged groups, but conclusions differ across the pairwise comparisons. For men, we cannot reject the null hypothesis for pairwise comparisons between ˇ1 D ˇ2 and ˇ2 D ˇ3 for almost all age groups. However, we reject for all age groups the null hypothesis that ˇ3 D ˇ4 , ˇ2 D ˇ4 , and ˇ1 D ˇ4 , except for the youngest and oldest age groups. Individuals in age groups 41–50 and 51–60 are those for whom equality of the coefficients is rejected most often (four out of six cases). The oldest and the youngest age groups (16–30, 71 and older) are the two groups for whom heterogeneity in the effect of income on health satisfaction plays the least important role. For women, heterogeneity also plays the most important role for individuals in the middle-aged groups. Heterogeneity is rejected for the two oldest age groups, though. For these two age groups, it would be sufficient to apply a conditional ordered fixed-effects logit specification. These results are interpreted as follows: income affects individuals differently, depending on whether they perceive their own health as bad/poor or as good/very good. Differential effects of income also play a role for individuals who perceive their health as good or very good. Income has, however, the same effect on perceived health when the individual perceives health as poor or bad. 7 In Table V columns 1–4 show the results when using the threshold values j D 1 to j D 4 to dichotomise the dependent variable (assuming heterogeneity), whereas columns 5 and 6 show the results when using the mean and the median (assuming homogeneity), respectively, to dichotomise the dependent variable. The model using the median of health satisfaction as cut-off value to dichotomise the ordered dependent variable avoids problems associated with the arbitrary scaling of the ordered variable. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 560 A. M. JONES AND S. SCHURER Table I. Test for heterogeneity in income coefficients for sample of men Pairwise tests of age-specific income coefficients that result from different threshold js ˇ1 D ˇ2 ˇ2 D ˇ3 ˇ3 D ˇ4 ˇ1 D ˇ4 ˇ2 D ˇ4 ˇ1 D ˇ3 Income age group 16–30 0.44 2 1 0.5056 Prob. > 2 Income age group 31–40 1.34 0.2477 1.44 0.2300 4.05 0.0443 4.39 0.0361 2.08 0.1490 0.03 2 1 Prob. > 2 0.8564 Income age group 41–50 0.45 0.5036 9.20 0.0024 5.74 0.0166 10.16 0.0014 0.42 0.5154 3.40 2 1 0.0650 Prob. > 2 Income age group 51–60 3.50 0.1689 3.50 0.0615 16.45 0.0000 8.65 0.0033 8.61 0.0033 2.29 2 1 0.1302 Prob. > 2 Income age group 61–70 2.83 0.0927 3.59 0.0582 16.14 0.0001 10.11 0.0015 8.24 0.0041 0.14 2 1 0.7051 Prob. > 2 Income age group 71 and older 0.01 0.9057 8.37 0.0038 7.58 0.0059 8.26 0.0040 0.23 0.6287 2 1 Prob. > 2 2.26 0.1323 0.11 0.7416 1.94 0.1632 0.67 0.4148 4.34 0.0372 0.64 0.4249 Note: Columns 1–6 report the 2 statistic and the p-value of the hypothesis that coefficients of income across different thresholds of satisfaction with health are pairwise the same for men. Column 7 reports the same statistic for the hypothesis that all four income coefficients are equal. The null hypothesis of homogeneity is not rejected if the p-value >0.10. The method used for testing equality of two coefficients is taken from Allen McDowell, Stata Corp, July 2005. http://www.stata.com/support/faqs/stat/testing.html. 4.3. Marginal Effects of Income In this section the marginal effects and their confidence intervals for the logarithm of net monthly household equivalent income are reported for each age-specific subgroup. The main hypothesis is that the correlation between the individual fixed effect and socioeconomic status increases over the life cycle since the magnitude of the individual fixed effect grows over time. Therefore, the parameter bias is expected to be greater for older age groups; the difference in the marginal effects calculated for the POL and the CFEL should be no smaller for the older age groups than for the younger ones. In a first step, we look at reports of very good health satisfaction; i.e. in the case of the POL, the probability of reporting very good health satisfaction, and in the case of the REL and CFEL the probability of reporting at least once a health satisfaction level greater than 4. These results are contrasted with the probability of reporting a health satisfaction level beyond bad or poor to assess whether there are asymmetries in the effect of income on health satisfaction. Figure 3 shows the box-plots of the marginal effects of log-income on the probability of reporting very good health satisfaction and their confidence intervals for each age group (Figure 3(a)–(f)). The dot in the figure represents the magnitude of the marginal effect, while the vertical, capped lines represent the upper and the lower bound of a 95% confidence interval. The marginal effects Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 561 HETEROGENEITY AND HEALTH SATISFACTION Table II. Test for heterogeneity in income coefficients for sample of women Pairwise test of equality of age-specific income coefficients ˇ1 D ˇ2 D ˇ1 D ˇ2 ˇ2 D ˇ3 ˇ3 D ˇ4 ˇ1 D ˇ4 ˇ2 D ˇ4 ˇ1 D ˇ3 ˇ3 D ˇ4 Income age group 16–30 2.36 2 1 0.1246 Prob. > 2 Income age group 31–40 0.66 0.4163 9.20 0.0024 13.60 0.0002 10.21 0.0014 4.71 0.0299 22.30 0.0001 3.72 2 1 Prob. > 2 0.0537 Income age group 41–50 0.23 0.6295 0.05 0.8208 4.84 0.0278 0.07 0.7862 5.62 0.0178 5.80 0.1217 6.75 2 1 0.0094 Prob. > 2 Income age group 51–60 4.29 0.0383 5.06 0.0245 30.77 0.0000 14.98 0.0001 18.17 0.0000 35.54 0.0000 3.39 2 1 0.0655 Prob. > 2 Income age group 61–70 8.31 0.0039 0.01 0.9308 13.43 0.0002 5.75 0.0165 17.22 0.0000 23.19 0.0000 0.04 0.38 2 1 0.8325 0.5370 Prob. > 2 Income age group 71 and older 0.17 0.6825 0.01 0.9109 0.01 0.9321 0.07 0.7899 0.42 0.9356 2 1 Prob. > 2 0.06 0.8002 0.93 0.3339 0.01 0.9331 0.92 0.3380 1.96 0.5814 1.83 0.1765 0.22 0.6399 Note: Columns 1–6 report the 2 statistic and the p-value of the hypothesis that coefficients of income across different thresholds of satisfaction with health are pairwise the same for women. Column 7 reports the same statistic for the hypothesis that all four income coefficients are equal. The null hypothesis of homogeneity is not rejected if the p-value >0.10. The method used for testing equality of two coefficients is taken from Allen McDowell, Stata Corp, July 2005. http://www.stata.com/support/faqs/stat/testing.html. for men (women) are indicated by an M (W) on the horizontal axis. From left to right, each chart reports the box-plot resulting from the POL, the REL, and the CFEL model. The marginal effect is greatest using the estimated coefficients from the POL models for both men and women alike, but the effect tends to be slightly greater for women among the younger age groups and smaller for the older age groups than for men. For both men and women in the middle-aged groups (31–40, 41–50, and 51–60) each additional unit of the logarithm of income translates into a greater probability of reporting very good health satisfaction by 4–6 percentage points. For instance, all things being equal, a doubling of log-income per month will increase the probability to report very good health by about 6 percentage points for the male age group 51–60.8 The effect is smallest for the youngest (0.015, Figure 3(a)) and the oldest age group (0.03, Figure 3(f)). In contrast, the marginal effect of log-income obtained from the CFEL differs more strongly between men and women and generally converges to zero. For men, it is either zero (age groups 16–30, 41–50, 51–60, and 71 and older) or negative (age groups 31–40 and 61–70). For women, the marginal effect is also either zero (age groups 41–50, 61–70, and 71 and older), positive (age 8A 1% increase in log-income increases the probability of reporting very good health by 0.06. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 562 A. M. JONES AND S. SCHURER (a) REL CFEL (b) POL REL CFEL .05 P(SWH>4) –.05 0 0 –.06 –.04 –.02 P(SWH>4) .02 .1 .04 POL M F M F M F M F Age group 16–30 CFEL (d) POL REL CFEL –.05 F M F M F M F Age group 41–50 F M F CFEL (f) POL REL CFEL .05 0 –.1 –.1 –.05 0 P(SWH>4) .05 .1 REL .1 POL M Age group 51–60 –.05 P(SWH>4) F .05 P(SWH>4) .05 0 –.05 P(SWH>4) M (e) M .1 REL .1 POL F 0 (c) M Age group 31–40 M F M F Age group 61–70 M F M F M F M F Age group 71 Figure 3. Marginal effects of income on the probability of reporting the highest value of satisfaction with health for both men (M) and women (W) obtained from three different models: pooled ordered logit (POL), random-effects logit (REL), and conditional fixed-effects logit (CFEL) groups 31–40 and 51–60), or negative (age group 16–30). The magnitude of the marginal effects obtained from the REL lies between those obtained from the POL and the CFEL. The fewer restrictions we impose on the model concerning unobserved heterogeneity, the smaller the effect of a marginal increase of income on the probability of reporting very good health. This Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae HETEROGENEITY AND HEALTH SATISFACTION 563 last result highlights one important finding in favour of choosing methodology prudently: once the individual fixed effect is controlled for and allowed to correlate with regressors in the model, the influence of observable socioeconomic status on very good self-reported health disappears. This decrease is the largest for the middle-aged and older groups (41–50, 51–60, and 61–70). For these groups the difference between the marginal effects of income between the POL and CFEL model lies between 6 and 10 percentage points for men. For women, the difference is slightly smaller. The effect is less marked for the youngest age group of 16–30 years old (and for women also for 31–40 years old). This result strengthens our hypothesis that the influence of the individual fixed effect plays a greater role in mediating the relationship between income and health status in older age. It is notable that the marginal effects of log-income on the probability of reporting health satisfaction levels beyond bad or poor do not disappear once controlling for unobserved heterogeneity. As illustrated in Figure 4, for men the marginal effect obtained from the CFEL takes values between 2.5 and 5 percentage points for all age groups except for the oldest group. For women, the effect is slightly smaller and becomes zero for the two oldest age groups. Also, for the two youngest age groups, the estimated difference in the marginal effects between the POL and the CFEL is relatively small (less than 2 percentage points, and no difference for women in age group 31–40), whereas this difference grows in the older age group (up to 12 percentage points). These results provide additional evidence in favour of the hypothesis that the omitted variable bias increases with age. 4.4. Predicted Probabilities A similar picture emerges when studying the predicted probabilities of reporting very good health satisfaction for the three models in Figure 5. In these figures we graph the change in reporting probabilities over a range of potential net monthly household incomes from ¤500 to ¤5500. The predicted probabilities for both men and women make it clear that the overall effect of income on very good health is relatively small. At maximum, giving an extra ¤5000 per month to a poor person in any middle-aged group raises the probability to report very good health by 20 percentage points in the POL (Figure 5(a) and (b)), and by 10 percentage points in the REL (Figure 5(c) and (d)). For the youngest and the oldest groups these effects are even less. Once individual-specific heterogeneity is controlled for, as illustrated in Figure 5(e) and (f), income does not have any effect on the probability of reporting very good health satisfaction. A sole exception are women aged 31–40 and 51–60, who still experience an increase of 8 percentage points. In contrast, additional income increases quite substantially the probability of reporting a health satisfaction level beyond bad or poor for almost all age groups in all models (Figure 6). In the POL, an additional ¤5000 in household income increases the probability of reporting better than the lowest levels of health satisfaction by more than 22 percentage points, even for the oldest age group. The two youngest age groups remain unaffected, though. Similar effects of half the magnitude are obtained from the REL models for both men and women. Once controlling for unobserved heterogeneity in the CFEL, an additional ¤5000 increases the probability of reporting better health satisfaction levels than bad or poor by almost 10 percentage points for both men and women, except for the oldest age group. These results suggest that despite individual-specific differences in reporting behaviour increased levels of income for middle-aged individuals raise levels of perceived health. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 564 A. M. JONES AND S. SCHURER (a) CFEL (b) POL REL CFEL .04 P(SWH>2) .02 .03 .02 0 0 .01 P(SWH>2) .04 .06 REL .05 POL M F M F M F M F Age group 16 to 30 CFEL (d) F POL REL CFEL .08 P(SWH>2) .1 .06 .05 .04 .02 .02 .04 .03 P(SWH>2) M F M F M F M F F M F CFEL (f) POL REL CFEL .05 0 .05 P(SWH>2) .1 .05 0 P(SWH>2) .1 .15 REL .15 POL M Age group 51–60 Age group 41–50 (e) M .12 REL .07 POL F .06 (c) M Age group 31–40 M F M F M F Age group 61–70 M F M F M F Age group 71 Figure 4. Marginal effects of income on the probability to report satisfaction with health greater than two for both men (M) and women (W) obtained from three different models: pooled ordered logit (POL), randomeffects logit (REL), and conditional fixed-effects logit (CFEL) 4.5. Robustness Checks of Marginal Effects Figures 7 and 8 display the distribution of the approximated individual fixed effect, which we calculated according to equation (17) and averaged for each age group according to equation (18). The different figures illustrate to what degree the arbitrary assumption of scaling the individual Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 565 .2 .1 .2 Pr(SWH = 5) .3 .3 .4 (b) 0 0 .1 Pr(SWH = 5) (a) .4 HETEROGENEITY AND HEALTH SATISFACTION 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 Monthly Income (in Euro) Monthly Income (in Euro) 16 to 30 51 to 60 31 to 40 61 to 70 41 to 50 71 and older 16 to 30 51 to 60 41 to 50 71 and older Pol (women) .3 0 .2 .1 .2 Pr(SWH = 5) .4 .3 Pr(SWH = 5) .4 (e) .5 .5 Pol (men) (d) 31 to 40 61 to 70 500 1500 2500 3500 4500 5500 500 1500 Monthly Income (in Euro) 16 to 30 51 to 60 31 to 40 61 to 70 2500 16 to 30 51 to 60 41 to 50 71 and older 4500 5500 31 to 40 61 to 70 41 to 50 71 and older REL (women) .35 .5 .4 .45 Pr(SWH = 5) .6 .55 Pr(SWH = 5) .5 (f) .55 .65 REL (men) (e) 3500 Monthly Income (in Euro) 500 1500 2500 3500 4500 5500 Monthly Income (in Euro) 16 to 30 51 to 60 31 to 40 61 to 70 CFEL (men) 500 1500 2500 3500 4500 5500 Monthly Income (in Euro) 41 to 50 71 and older 16 to 30 51 to 60 31 to 40 61 to 70 41 to 50 71 and older CFEL (women) Figure 5. Simulation of the probability of reporting the highest level of satisfaction with health for changes in income from ¤500 to ¤5500 for three different models: pooled ordered logit (POL), random-effects logit (REL), and conditional fixed-effects logit (CFEL) for both men and women. This figure is available in color online at wileyonlinelibrary.com/journal/jae Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 566 .9 .8 Pr(SWH > 2) .6 .7 .8 .6 .7 Pr(SWH > 2) 1 1 (b) .9 (a) A. M. JONES AND S. SCHURER 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 Monthly Income (in Euro) 16 to 30 51 to 60 31 to 40 61 to 70 Monthly Income (in Euro) 41 to 50 71 and older 16 to 30 51 to 60 31 to 40 61 to 70 41 to 50 71 and older POL (women) (d) .2 .4 .4 .6 Pr(SWH > 2) .6 .5 Pr(SWH > 2) .8 .7 (c) 1 POL (men) 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 Monthly Income (in Euro) Monthly Income (in Euro) 16 to 30 51 to 60 31 to 40 61 to 70 41 to 50 71 and older 16 to 30 51 to 60 41 to 50 71 and older REL (women) .88 .82 .75 .84 .86 Pr(SWH > 2) .85 .8 Pr(SWH > 2) .9 .9 (f) .92 REL (men) (e) 31 to 40 61 to 70 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 Monthly Income (in Euro) 16 to 30 51 to 60 31 to 40 61 to 70 CFEL (men) 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 Monthly Income (in Euro) 41 to 50 71 and older 16 to 30 51 to 60 31 to 40 61 to 70 41 to 50 71 and older CFEL (women) Figure 6. Simulation of the probability of reporting satisfaction with health better than bad and poor for changes in income from ¤500 to ¤5500 for three different models: pooled ordered logit (POL), random effects logit (REL), and conditional fixed-effects logit (CFEL) for both men and women. This figure is available in color online at wileyonlinelibrary.com/journal/jae Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 567 HETEROGENEITY AND HEALTH SATISFACTION .3 (b) .2 Density .1 .2 0 0 .1 Density .3 (a) .4 fixed effect to zero for calculating the marginal effects of income is sensible for varying threshold values j and the different age groups (here we depict only the distributions for threshold values j D 2 and j D 4). For both men and women the distribution of the individual fixed effect is centred around zero for the three younger age groups and slightly tilted to the left of zero for the three older age groups. The degree of skewness depends on the threshold value j: the smaller the threshold value, the more the distribution is moved to the left of zero for the three older age groups. For these cases, we would expect the zero value assumption to bias the calculation of the marginal effects the most. Figures 9 and 10 confirm the suggestion that only the effects of income on the probability of reporting satisfaction with health beyond bad and poor (SWH > 2) for the older age groups should be different. The first column of the box-plot depicts the original marginal effect obtained from a conditional fixed-effects model that assumes the individual fixed effect to be zero. The second column depicts the marginal effects obtained from the same model, except for using the approximated value of the individual fixed effect. –6 –4 –2 0 2 4 –5 0 x x 16 to 30 41 to 50 61 to 70 31 to 40 51 to 60 71 and older 5 16 to 30 41 to 50 61 to 70 Threshold value j = 2 31 to 40 51 to 60 71 and older Threshold value j = 4 .3 (b) .2 Density .1 .2 0 0 .1 Density .3 (a) .4 Figure 7. Probability distribution of individual fixed effect obtained from the conditional fixed-effects logit (CFEL), when the threshold values are j D 2 and j D 4 for the sample of men –6 –4 –2 0 2 4 –5 0 x x 16 to 30 41 to 50 61 to 70 31 to 40 51 to 60 71 and older Threshold value j = 2 16 to 30 41 to 50 61 to 70 5 31 to 40 51 to 60 71 and older Threshold value j = 4 Figure 8. Probability distribution of individual fixed effect obtained from the conditional fixed effects logit (CFEL), when the threshold values are j D 2 and j D 4 for the sample of women Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 568 A. M. JONES AND S. SCHURER (b) .04 –.04 –.02 –.06 M F M F M ALT ME (d) F ORIGINAL ALT ME .04 .02 –.04 –.02 0 P(SWH>4) .02 0 P(SWH>4) –.02 –.04 M F M F M Age group 41–50 (e) M .06 .04 ORIGINAL F Age group 31–40 Age group 16–30 (c) ALT ME .02 P(SWH>4) 0 –.02 –.04 P(SWH>4) ORIGINAL .06 ALT ME .02 ORIGINAL 0 (a) M F ALT ME (f) ORIGINAL ALT ME –.1 –.05 0 P(SWH>4) 0 –.05 –.1 P(SWH>4) .05 .05 .1 ORIGINAL F Age group 51–60 M F M Age group 61–70 F M F M F Age group 71 Figure 9. Robustness checks of marginal effects of income obtained from the conditional fixed effects logit (CFEL) on the probability of reporting the highest value of satisfaction with health For instance, for men aged between 51 and 60 the marginal effect of income on the probability of reporting health better than bad and poor is almost 2 percentage points greater in the alternative calculation than when assuming a zero individual fixed effect (Figure 10(d)). Similar differences are obtained for men in the 61–70 age group. For women these differences are also present for the same age groups, but smaller in magnitude (1 percentage point difference). Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 569 HETEROGENEITY AND HEALTH SATISFACTION (a) ALT ME (b) ORIGINAL ALT ME .04 P(SWH>2) .02 .03 .02 0 0 .01 P(SWH>2) .04 .06 .05 ORIGINAL M F M F M Age group 16–30 ALT ME (d) .04 F M F M Age group 41–50 M F ALT ME (f) ORIGINAL ALT ME 0 P(SWH>2) .04 .02 –.05 .06 .08 .05 ORIGINAL F Age group 51–60 –.02 –.1 0 P(SWH>2) ALT ME .1 ORIGINAL .02 M (e) F .08 P(SWH>2) .06 .04 .02 P(SWH>2) .08 ORIGINAL M .06 (c) F Age group 31–40 M F M F M F Age group 61–70 M F Age group 71 Figure 10. Robustness checks of marginal effects of income obtained from the conditional fixed effects logit (CFEL) on the probability of reporting satisfaction with health better than bad or poor 5. SUMMARY AND CONCLUSION Choosing the right econometric model for accurately testing the socioeconomic gradient of health is quite a challenging task for the applied researcher, given that unobserved factors play such a dominant role in influencing both socioeconomic status and health outcomes. The literature so far has concentrated on controlling for time-invariant unobserved heterogeneity in nonlinear models, Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae 570 A. M. JONES AND S. SCHURER which reduces the options either to conditional fixed effects estimation by dichotomising the categorical dependent variable or to impose orthogonality between the unobserved heterogeneity and regressors of the model. Some papers applied threshold-specific models, but failed to treat the difficulty of identification, as emphasised by Cunha et al. (2007) and Ronning (1990). Little attention has been paid in the literature to these identification problems while controlling for omitted variable and reporting bias. We applied a conditional fixed-effects logit model to estimate the socioeconomic gradient in health satisfaction while allowing for threshold-specific, time-invariant heterogeneity. Such a formulation complies with the stochastic monotonicity requirement and allows us to test three hypotheses: first, whether income influences health satisfaction in a heterogeneous fashion; second, whether this impact differs across age groups, and third, whether assumptions imposed on the relationship between unobserved heterogeneity and socioeconomic status in assessing health satisfaction make a larger practical difference for older age groups. To illustrate our point, we estimate a model of health satisfaction using 22 waves of the GSOEP. On the one hand, we find that imposing a homogeneous relationship between income and health satisfaction, independent of whether time-invariant individual heterogeneity is controlled for or not, is too restrictive. That is to say, that the pooled ordered logit and the conditional ordered fixedeffects logit (Ferrer-i-Carbonell and Frijters, 2004) do not sufficiently account for the heterogeneity in the data, and thus conclusions about the potential effects of income on health can be misleading. On the other hand, ignoring individual- and threshold-specific heterogeneity, which may represent cognitive ability that determines perception and judgement of one’s own health, leads to an overestimation of the effect of income on health, especially for the effect of income on reports of very good health. Once controlling for individual-specific effects, income does not exert an independent effect. However, income helps to increase reports of health satisfaction for changes at the lower end of the health distribution. The overstatement of the income effect is stronger for the older age groups, supporting the hypothesis that individual-specific factors such as perception and cognitive ability play a greater role in determining health in older age. Our robustness checks indicate that the zero value assumption on the individual fixed effects used for calculating the marginal effects of income does not matter substantially. If at all, it matters for older age groups when calculating the marginal effect for the probability of reporting health satisfaction greater than bad or poor. We suggest that marginal effects in conditional fixed-effects logits are reliable under the zero value assumption, especially if marginal effects are averaged across several age groups. ACKNOWLEDGEMENTS The results reported in this paper were generated using STATA SE 10.2. The programs are available from the authors upon request. Grant sponsor was the Thyssen Krupp von Halbach Foundation. We thank two anonymous referees and Steven N. Durlauf for very helpful comments. We also thank Nigel Rice, Jan Brenner, Paul Frijters, Pilar Garcı́a Gomez, John Haisken-DeNew, Michael Shields, and participants of the Health, Econometrics, and Data Group at the University of York, UK, the Brown Bag Seminar at the RWI Essen, Essen, Germany, the First Doctoral Conference of the RGS in Economics, University of Dortmund, Germany, the International Association of Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae HETEROGENEITY AND HEALTH SATISFACTION 571 Health Economics (IHEA), Copenhagen, Denmark, and the Chair of Empirical Economics and Statistics, University of Zurich, Switzerland. All errors are our own. REFERENCES Almond D. 2006. Is the 1918 influenza pandemic over? 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JONES AND S. SCHURER APPENDIX Table III. Summary statistics for men and women Variable Men East Germany Age group 31–40 Age group 41–50 Age group 51–60 Age group 61–70 Age group 71 and older Income age group 1630 Income age group 3140 Income age group 4150 Income age group 5160 Income age group 6170 Income age group 71 No. years of education Registered unemployed Hours worked overtime Work disability Divorced, separated, or widowed Single, never married Number of person in household Women East Germany Age group 31–40 Age group 41–50 Age group 51–60 Age group 61–70 Age group 71 and older Income age group 1630 Income age group 3140 Income age group 4150 Income age group 5160 Income age group 6170 Income age group 71 No. years of education Registered unemployed Hours worked overtime Work disability Divorced, separated, or widowed Single, never married Number of person in household Mean SD Min. Max. N 0.219 0.199 0.182 0.158 0.122 0.072 1.858 1.398 1.295 1.127 0.866 0.512 11.4 0.072 1.572 0.033 0.075 0.272 3.049 0.413 0.399 0.386 0.365 0.327 0.259 3.097 2.811 2.749 2.612 2.328 1.836 2.993 0.258 3.454 0.178 0.264 0.445 1.368 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 10.366 9.782 10.366 10.801 11.082 10.473 18 1 56.1 1 1 1 17 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 134,626 0.223 0.2 0.18 0.148 0.125 0.102 1.701 1.398 1.28 1.049 0.877 0.709 10.946 0.064 0.59 0.024 0.173 0.206 2.903 0.416 0.4 0.384 0.355 0.331 0.303 2.995 2.806 2.743 2.529 2.325 2.103 2.789 0.245 1.926 0.153 0.378 0.405 1.397 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 10.801 10.254 10.366 11.166 10.656 10.473 18 1 68 1 1 1 17 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 149,030 Note: Summary statistics for year dummy variables are omitted. Copyright 2009 John Wiley & Sons, Ltd. J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae Copyright 2009 John Wiley & Sons, Ltd. Income age group 71 Income age group 6170 Income age group 5160 Income age group 4150 Income age group 3140 Income age group 1630 Age group 71 and older Age group 61–70 Age group 51–60 Age group 41–50 Age group 31–40 Men East Germany 0.150 (0.026)ŁŁŁ 1.786 (0.330)ŁŁŁ 3.624 (0.360)ŁŁŁ 5.386 (0.362)ŁŁŁ 5.483 (0.390)ŁŁŁ 4.665 (0.582)ŁŁŁ 0.062 (0.031)ŁŁ 0.235 (0.042)ŁŁŁ 0.430 (0.043)ŁŁŁ 0.616 (0.043)ŁŁŁ 0.610 (0.048)ŁŁŁ 0.451 (0.078)ŁŁŁ Ordered logit Estimated thresholds 0.073 (0.070) 2.863 (0.981)ŁŁŁ 5.178 (0.938)ŁŁŁ 5.662 (0.881)ŁŁŁ 4.906 (0.951)ŁŁŁ 2.368 (1.025)ŁŁ 0.306 (0.103)ŁŁŁ 0.626 (0.107)ŁŁŁ 0.863 (0.095)ŁŁŁ 0.838 (0.081)ŁŁŁ 0.695 (0.095)ŁŁŁ 0.201 (0.109)Ł jD1 0.043 (0.048) 1.565 (0.592)ŁŁŁ 3.221 (0.578)ŁŁŁ 4.548 (0.559)ŁŁŁ 4.632 (0.614)ŁŁŁ 2.935 (0.724)ŁŁŁ 0.230 (0.062)ŁŁŁ 0.385 (0.066)ŁŁŁ 0.517 (0.060)ŁŁŁ 0.614 (0.055)ŁŁŁ 0.603 (0.065)ŁŁŁ 0.273 (0.085)ŁŁŁ jD2 0.268 (0.040)ŁŁŁ 2.070 (0.413)ŁŁŁ 3.283 (0.427)ŁŁŁ 5.204 (0.434)ŁŁŁ 5.849 (0.489)ŁŁŁ 4.328 (0.630)ŁŁŁ 0.139 (0.042)ŁŁŁ 0.361 (0.048)ŁŁŁ 0.434 (0.048)ŁŁŁ 0.603 (0.048)ŁŁŁ 0.662 (0.057)ŁŁŁ 0.367 (0.080)ŁŁŁ jD3 0.373 (0.044)ŁŁŁ 1.360 (0.401)ŁŁŁ 3.602 (0.454)ŁŁŁ 6.122 (0.506)ŁŁŁ 6.656 (0.622)ŁŁŁ 5.495 (0.865)ŁŁŁ 0.058 (0.037) 0.048 (0.050) 0.277 (0.057)ŁŁŁ 0.539 (0.063)ŁŁŁ 0.558 (0.081)ŁŁŁ 0.340 (0.118)ŁŁŁ jD4 0.141 (0.023)ŁŁŁ 0.051 (0.295) 0.603 (0.306)ŁŁ 1.553 (0.307)ŁŁŁ 1.377 (0.349)ŁŁŁ 1.610 (0.442)ŁŁŁ 0.042 (0.028) 0.037 (0.035) 0.032 (0.036) 0.143 (0.036)ŁŁŁ 0.146 (0.042)ŁŁŁ 0.151 (0.057)ŁŁŁ j D mean Random effects logits Threshold j used to dichotomise SWH Table IV. Ordered and random effects logits 0.257 (0.028)ŁŁŁ 0.385 (0.354) 0.265 (0.365) 1.364 (0.366)ŁŁŁ 1.534 (0.414)ŁŁŁ 1.474 (0.527)ŁŁŁ 0.098 (0.033)ŁŁŁ 0.158 (0.043)ŁŁŁ 0.063 (0.043) 0.083 (0.043)Ł 0.132 (0.050)ŁŁŁ 0.106 (0.069) j D median HETEROGENEITY AND HEALTH SATISFACTION 575 J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae Copyright 2009 John Wiley & Sons, Ltd. Income age group 1630 Age group 71 and older Age group 61–70 Age group 51–60 Age group 41 to 50 Age group 31–40 Observations Women East Germany Constant Work disability Hours worked overtime Registered unemployed No. years of education 0.117 (0.043)ŁŁŁ 1.619 (0.508)ŁŁŁ 3.248 (0.507)ŁŁŁ 4.957 (0.499)ŁŁŁ 3.115 (0.536)ŁŁŁ 2.427 (0.555)ŁŁŁ 0.179 (0.054)ŁŁŁ 0.021 (0.061) 1.137 (0.856) 4.128 (0.811)ŁŁŁ 4.873 (0.782)ŁŁŁ 2.610 (0.824)ŁŁŁ 0.928 (0.802) 0.387 (0.090)ŁŁŁ 0.150 (0.025)ŁŁŁ 2.302 (0.300)ŁŁŁ 3.466 (0.338)ŁŁŁ 4.934 (0.333)ŁŁŁ 4.343 (0.368)ŁŁŁ 3.199 (0.444)ŁŁŁ 0.088 (0.030)ŁŁŁ 134 626 0.026 (0.006)ŁŁŁ 0.337 (0.042)ŁŁŁ 0.017 (0.004)ŁŁŁ 1.192 (0.046)ŁŁŁ 1.906 (0.440)ŁŁŁ 134 626 jD2 0.063 (0.010)ŁŁŁ 0.398 (0.062)ŁŁŁ 0.031 (0.007)ŁŁŁ 1.468 (0.063)ŁŁŁ 3.142 (0.730)ŁŁŁ 134 626 jD1 0.288 (0.037)ŁŁŁ 1.799 (0.368)ŁŁŁ 3.127 (0.385)ŁŁŁ 4.475 (0.397)ŁŁŁ 4.562 (0.440)ŁŁŁ 2.374 (0.494)ŁŁŁ 0.155 (0.038)ŁŁŁ 0.029 (0.005)ŁŁŁ 0.263 (0.035)ŁŁŁ 0.003 (0.003) 1.065 (0.044)ŁŁŁ 0.484 (0.302) 134 626 jD3 0.348 (0.042)ŁŁŁ 3.107 (0.374)ŁŁŁ 3.666 (0.433)ŁŁŁ 6.554 (0.487)ŁŁŁ 6.512 (0.571)ŁŁŁ 3.375 (0.697)ŁŁŁ 0.067 (0.036)Ł 0.030 (0.005)ŁŁŁ 0.101 (0.041)ŁŁ 0.003 (0.003) 0.832 (0.064)ŁŁŁ 0.498 (0.268)Ł 134 626 jD4 0.114 (0.021)ŁŁŁ 0.506 (0.267)Ł 0.551 (0.279)ŁŁ 1.377 (0.284)ŁŁŁ 0.736 (0.313)ŁŁ 1.272 (0.339)ŁŁŁ 0.036 (0.026) 0.004 (0.003) 0.079 (0.027)ŁŁŁ 0.006 (0.002)ŁŁŁ 0.670 (0.037)ŁŁŁ 0.146 (0.202) 134 915 j D mean Random effects logits Threshold j used to dichotomise SWH 0.011 (0.004)ŁŁŁ 0.269 (0.032)ŁŁŁ 0.000 (0.002) 1.165 (0.033)ŁŁŁ Ordered logit Estimated thresholds Table IV. (Continued ) 0.131 (0.025)ŁŁŁ 0.253 (0.318) 0.880 (0.331)ŁŁŁ 1.382 (0.339)ŁŁŁ 0.764 (0.368)ŁŁ 0.713 (0.396)Ł 0.104 (0.031)ŁŁŁ 0.024 (0.004)ŁŁŁ 0.063 (0.033)Ł 0.005 (0.002)ŁŁ 0.486 (0.046)ŁŁŁ 0.990 (0.241)ŁŁŁ 134 915 j D median 576 A. M. JONES AND S. SCHURER J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae Copyright 2009 John Wiley & Sons, Ltd. 149,030 0.341 (0.036)ŁŁŁ 0.438 (0.039)ŁŁŁ 0.587 (0.038)ŁŁŁ 0.489 (0.045)ŁŁŁ 0.255 (0.057)ŁŁŁ 0.029 (0.004)ŁŁŁ 0.258 (0.029)ŁŁŁ 0.009 (0.004)ŁŁ 1.167 (0.036)ŁŁŁ 0.476 (0.094)ŁŁŁ 0.811 (0.080)ŁŁŁ 0.827 (0.074)ŁŁŁ 0.478 (0.083)ŁŁŁ 0.091 (0.078) 0.062 (0.009)ŁŁŁ 0.241 (0.063)ŁŁŁ 0.035 (0.011)ŁŁŁ 1.402 (0.067)ŁŁŁ 2.402 (0.634)ŁŁŁ 149,030 jD1 0.338 (0.056)ŁŁŁ 0.496 (0.053)ŁŁŁ 0.654 (0.051)ŁŁŁ 0.371 (0.058)ŁŁŁ 0.163 (0.062)ŁŁŁ 0.043 (0.006)ŁŁŁ 0.228 (0.040)ŁŁŁ 0.005 (0.006) 1.121 (0.049)ŁŁŁ 1.853 (0.383)ŁŁŁ 149,030 jD2 0.333 (0.043)ŁŁŁ 0.430 (0.043)ŁŁŁ 0.524 (0.044)ŁŁŁ 0.498 (0.052)ŁŁŁ 0.090 (0.061) 0.050 (0.005)ŁŁŁ 0.192 (0.033)ŁŁŁ 0.005 (0.004) 0.936 (0.048)ŁŁŁ 0.003 (0.274) 149,030 jD3 0.285 (0.046)ŁŁŁ 0.266 (0.053)ŁŁŁ 0.565 (0.061)ŁŁŁ 0.529 (0.074)ŁŁŁ 0.004 (0.095) 0.002 (0.005) 0.118 (0.041)ŁŁŁ 0.014 (0.005)ŁŁŁ 0.762 (0.073)ŁŁŁ 0.814 (0.261)ŁŁŁ 149,030 jD4 0.025 (0.031) 0.025 (0.032) 0.122 (0.032)ŁŁŁ 0.059 (0.038) 0.101 (0.042)ŁŁ 0.017 (0.003)ŁŁŁ 0.049 (0.026)Ł 0.003 (0.003) 0.535 (0.039)ŁŁŁ 0.258 (0.189) 149,374 j D mean Random effects logits Threshold j used to dichotomise SWH 0.071 (0.037)Ł 0.015 (0.038) 0.073 (0.039)Ł 0.015 (0.044) 0.003 (0.050) 0.009 (0.004)ŁŁ 0.020 (0.031) 0.004 (0.004) 0.382 (0.050)ŁŁŁ 0.998 (0.224)ŁŁŁ 149,374 j D median Note: Column 1 reports the coefficients obtained from a pooled ordered logit model, regressing the categorical variable health satisfaction on the full set of control variables. Columns 2–5 report the coefficients obtained from a random effects logit when dichotomising the dependent variable health satisfaction with threshold values j D 1, 2, 3, 4. Columns 6 and 7 report the estimated coefficients of a model that uses the mean and the median as threshold values. Coefficients for time dummy variables, marital status, and persons in household are omitted. Asterisks indicate significance at Ł 10% level, ŁŁ 5% level, and ŁŁŁ 1% level. Observations Constant Work disability Hours worked overtime Registered unemployed No. years of education Income age group 71 Income age group 6170 Income age group 5160 Income age group 4150 Income age group 3140 Ordered logit Estimated thresholds Table IV. (Continued ) HETEROGENEITY AND HEALTH SATISFACTION 577 J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae Copyright 2009 John Wiley & Sons, Ltd. Observations Work disability Hours worked overtime Registered unemployed No. years of eduction Income age group 71 Income age group 6170 Income age group 5160 Income age group 4150 Income age group 3140 Income age group 1630 Age group 71 and older Age group 61–70 Age group 51–60 Age group 41–50 Age group 31–40 Men East Germany 0.218 (0.389) 0.380 (1.193) 1.075 (1.195) 0.757 (1.157) 0.980 (1.247) 5.592 (1.438)ŁŁŁ 0.254 (0.138)Ł 0.266 (0.124)ŁŁ 0.507 (0.112)ŁŁŁ 0.483 (0.098)ŁŁŁ 0.297 (0.116)ŁŁ 0.388 (0.155)ŁŁ 0.012 (0.023) 0.278 (0.066)ŁŁŁ 0.026 (0.008)ŁŁŁ 1.102 (0.064)ŁŁŁ 29,058 jD1 0.038 (0.211) 0.355 (0.689) 0.636 (0.706) 1.006 (0.702) 0.218 (0.769) 3.084 (0.979)ŁŁŁ 0.148 (0.077)Ł 0.240 (0.075)ŁŁŁ 0.263 (0.070)ŁŁŁ 0.304 (0.066)ŁŁŁ 0.244 (0.078)ŁŁŁ 0.234 (0.116)ŁŁ 0.024 (0.013)Ł 0.216 (0.044)ŁŁŁ 0.014 (0.004)ŁŁŁ 0.908 (0.047)ŁŁŁ 61,511 jD2 0.052 (0.135) 0.826 (0.466)Ł 0.609 (0.510) 0.879 (0.528)Ł 1.048 (0.603)Ł 0.544 (0.845) 0.042 (0.050) 0.178 (0.054)ŁŁŁ 0.139 (0.057)ŁŁ 0.158 (0.057)ŁŁŁ 0.231 (0.069)ŁŁŁ 0.006 (0.109) 0.009 (0.008) 0.150 (0.036)ŁŁŁ 0.003 (0.003) 0.843 (0.045)ŁŁŁ 91,177 jD3 Thresholds j from 1 to 4 0.166 (0.133) 0.186 (0.457) 0.015 (0.568) 0.021 (0.662) 0.995 (0.844) 0.565 (1.297) 0.037 (0.043) 0.062 (0.058) 0.031 (0.071) 0.032 (0.083) 0.142 (0.109) 0.062 (0.175) 0.023 (0.007)ŁŁŁ 0.022 (0.044) 0.001 (0.003) 0.580 (0.065)ŁŁŁ 76,910 jD4 Table V. Estimated coefficients for various conditional fixed effects logits 0.131 (0.106) 0.610 (0.366)Ł 0.763 (0.407)Ł 1.445 (0.420)ŁŁŁ 1.071 (0.483)ŁŁ 0.274 (0.674) 0.041 (0.037) 0.058 (0.044) 0.079 (0.047)Ł 0.167 (0.047)ŁŁŁ 0.173 (0.057)ŁŁŁ 0.012 (0.088) 0.022 (0.006)ŁŁŁ 0.107 (0.030)ŁŁŁ 0.004 (0.002)Ł 0.720 (0.038)ŁŁŁ 121,664 j D mean 0.230 (0.127)Ł 0.802 (0.445)Ł 1.270 (0.488)ŁŁŁ 1.694 (0.502)ŁŁŁ 1.555 (0.571)ŁŁŁ 0.166 (0.796) 0.116 (0.045)ŁŁŁ 0.000 (0.053) 0.065 (0.056) 0.124 (0.056)ŁŁ 0.165 (0.067)ŁŁ 0.005 (0.103) 0.027 (0.007)ŁŁŁ 0.106 (0.036)ŁŁŁ 0.004 (0.003) 0.615 (0.047)ŁŁŁ 92,802 j D median Thresholds j mean or median 578 A. M. JONES AND S. SCHURER J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae Copyright 2009 John Wiley & Sons, Ltd. 0.328 (0.274) 0.304 (1.012) 1.631 (1.011) 0.930 (0.993) 2.985 (1.064)ŁŁŁ 4.860 (1.072)ŁŁŁ 0.311 (0.116)ŁŁŁ 0.411 (0.112)ŁŁŁ 0.620 (0.096)ŁŁŁ 0.534 (0.087)ŁŁŁ 0.046 (0.102) 0.243 (0.104)ŁŁ 0.038 (0.021)Ł 0.133 (0.067)ŁŁ 0.028 (0.012)ŁŁ 0.980 (0.068)ŁŁŁ 37,583 0.323 (0.160)ŁŁ 0.228 (0.584) 1.215 (0.610)ŁŁ 1.330 (0.614)ŁŁ 1.374 (0.672)ŁŁ 1.944 (0.725)ŁŁŁ 0.106 (0.066) 0.160 (0.065)ŁŁ 0.322 (0.062)ŁŁŁ 0.339 (0.059)ŁŁŁ 0.019 (0.070) 0.065 (0.081) 0.034 (0.011)ŁŁŁ 0.115 (0.042)ŁŁŁ 0.005 (0.006) 0.804 (0.050)ŁŁŁ 75,817 jD2 0.264 (0.118)ŁŁ 0.542 (0.413) 0.848 (0.449)Ł 0.603 (0.482) 0.076 (0.541) 1.253 (0.639)ŁŁ 0.041 (0.045) 0.121 (0.048)ŁŁ 0.159 (0.049)ŁŁŁ 0.110 (0.052)ŁŁ 0.078 (0.063) 0.118 (0.079) 0.024 (0.008)ŁŁŁ 0.064 (0.035)Ł 0.002 (0.005) 0.666 (0.048)ŁŁŁ 104,862 jD3 0.006 (0.124) 1.987 (0.426)ŁŁŁ 0.850 (0.529) 1.891 (0.638)ŁŁŁ 0.969 (0.770) 0.110 (1.005) 0.145 (0.042)ŁŁŁ 0.138 (0.053)ŁŁ 0.024 (0.065) 0.102 (0.079) 0.030 (0.099) 0.078 (0.135) 0.003 (0.007) 0.016 (0.044) 0.005 (0.005) 0.491 (0.076)ŁŁŁ 81,994 jD4 0.198 (0.095)ŁŁ 1.323 (0.335)ŁŁŁ 1.531 (0.368)ŁŁŁ 1.532 (0.389)ŁŁŁ 0.234 (0.436) 0.581 (0.507) 0.068 (0.035)Ł 0.119 (0.040)ŁŁŁ 0.150 (0.041)ŁŁŁ 0.148 (0.043)ŁŁŁ 0.021 (0.051) 0.095 (0.063) 0.013 (0.006)ŁŁ 0.058 (0.029)ŁŁ 0.003 (0.004) 0.589 (0.041)ŁŁŁ 136,738 j D mean 0.252 (0.112)ŁŁ 1.571 (0.399)ŁŁŁ 1.834 (0.436)ŁŁŁ 1.709 (0.461)ŁŁŁ 0.308 (0.511) 0.717 (0.590) 0.112 (0.041)ŁŁŁ 0.108 (0.048)ŁŁ 0.136 (0.049)ŁŁŁ 0.115 (0.051)ŁŁ 0.025 (0.060) 0.149 (0.073)ŁŁ 0.003 (0.007) 0.079 (0.035)ŁŁ 0.011 (0.005)ŁŁ 0.513 (0.051)ŁŁŁ 107,089 j D median Thresholds j mean or median Note: Columns 1–4 report the coefficients obtained from a conditional fixed-effects logit when dichotomising the dependent variable health satisfaction with threshold values j D 1, 2, 3, 4. Columns 5 and 6 report the estimated coefficients of a model that uses the mean and the median as threshold values. Coefficients for time dummy variables, marital status and persons in household are omitted. Asterisks indicate significance at Ł 10% level, ŁŁ 5% level, and ŁŁŁ 1% level. Observations Work disability Hours worked overtime Registered unemployed No. years of education Income age group 71 Income age group 6170 Income age group 5160 Income age group 4150 Income age group 3140 Income age group 1630 Age group 71 and older Age group 61–70 Age group 51–60 Age group 41–50 Age group 31–40 Women East Germany jD1 Thresholds j from 1 to 4 Table V. (Continued ) HETEROGENEITY AND HEALTH SATISFACTION 579 J. Appl. Econ. 26: 549–579 (2011) DOI: 10.1002/jae