Download Methods on Measuring Prices Links in the Fish Supply Chain Daniel

Methods on Measuring
Prices Links in the Fish Supply Chain
Daniel V. Gordon
Department of Economics
University of Calgary
FAO Workshop Value Chain
Tokyo, Japan
December 2010
• Introduction
• The demand for fish is derived by end-use
demand for the commodity.
• The retail price will reflect the fish price plus the
cost of marketing the commodity from the vessel
to the retail level.
• Let the retail/vessel price margin be the
difference between the retail and vessel price.
• The impact of a shock somewhere in the supply
chain on price will depend on the structure of the
relationship between the two sectors
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• Consider a fixed proportions relationship
between fish supply and marketing inputs
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• Add in market Demand
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• Assume that proportionally larger amounts of marketing
inputs are required to process increased supply of fish.
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• Supply of marketing inputs is perfectly elastic
but substitution possibilities exist between the
fish commodity and marketing inputs, the
derived fish demand curve is more elastic
• Wohlgenant and Haidacher (1989) argue that
processors can choose alternative production
processes, including different modes of
transporting, interproduct substitutability and
the substitution of quality for quantity.
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• Substitution
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• An interesting model by Wohlgenant (1989)
and Holloway (1991). Provides summary
measures of the price and margin flexibilities
M i   m   m m cMCi   m rd RDi   m qLi  1
pri   pr   prm cMCi   prrd RDi   prq Li   2
pf i   pf   pf MCi   pfrd RDi   pfq Li  1
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• Retail Demand Shift Variable and Marketing
Cost Index
• Consider the following price transmission
equation describing the stochastic behaviour
of fish prices.
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• The Rd shift variable is defined as the linear
combination:
• Why is it that we require premeasured
elasticities?
• The problem is statistically consistency.
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• The Rd index is deterministic and it might be
an advantage to introduce a stochastic error
term to account for unobserved randomness
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Estimated Elasticities
Estimated
Elasticity
Price of
Sirloin/kg
Price of
chicken/kg
Price of
Non-Food
Income
Population
0.25
0.15
0.09
0.81
1.0
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• Marketing Cost Index
• The Mc index is a weighted price index of the
cost of inputs used in moving fish product
through the supply chain. We have identified
four major inputs in fish processing; labour,
electricity, transportation and packaging. The
weights in the index reflect the cost share of
the input in the total cost of processing.
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Cost Share Major Inputs Fish Processing
Cost Share
Price of
Labour
0.51
Price of
Electricity
0.18
Price of
Transportation
0.16
Price of
Packaging
0.15
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• Mc index is written
• Combining the real price indices with the cost
shares we are able to predict the marketing
cost index for seafood processing
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• Reduced Form Models
• This price approach is based on the theory of
derived demand where the processed price of
fish is used as a proxy for market factors
setting the ex-vessel price.
• Univariate analysis is carried out on the exvessel price of fish.
• The ARMAX model is well identified and will
allow for dynamic forecasts of ex-vessel prices.
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• Selecting the correct lag specification critical
for generating an estimated equation with
good forecasting potential.
• Review the autocorrelation and partial
autocorrelation functions
• Candidate specifications defined on testing iid
• Box-Lung Q-statistic RMSE and AIC statistics.
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• ARMAX Model
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p
q
s 1
i 1
j 1
Exvesselt   o   p Ext    s Ds    Vi Exvesselt i    j  t  j   t
• Model with stationary variables
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• Error-Correction Modelling
• Recognizing the structural links between the
first-hand and processing, we postulate a
long-run price relationship.
• An error-correction (EC) model can be used to
econometrically identify both the short- and
long- run parameters for the first-hand market
and predict the length of time for price
adjustment to regain the long-run equilibrium
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• In a pairwise comparison of prices it is not
unreasonable to think of an economic
equilibrium describing the long-run
relationship and written in basic form as
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• in a short run distributed lag representation
the error-correction model can be written
• All arguments stationary
• The speed of adjustment to a short-run price
shock can be approximated
•
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• Testing weak exogeneity
• Long-run exogeneity tested by including the
error-correction term as an additional
regressor.
• Short-run exogeneity tested by using fitted
residuals from this equation and adding this
as an additional variable error correction
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