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GEOG 204 - Introductory GIS for the Social Sciences
28 September 2015
Neil Hanlon
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Census Geographical Units
Pros and Cons of Census Small Areas
Census Long Form Elimination
National Household Survey (2011 on)
Implications
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Census Backgrounder:
 Every five years
 2 questionnaires
▪ Short form (100%)
▪ Long form (20%)
▪ Mandatory prior to 2011
▪ Random sample
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Small area dissemination
Confidentiality and suppression
Units
 Block face
 Enumeration Areas
 Dissemination Areas (2001 on)
 Census Tracts
BLOCK FACE
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Area equivalent to a city
block bounded by
intersecting streets
These areas cover all of
Canada
Smallest geographic
area for which
population and dwelling
counts are disseminated
ENUMERATION AREAS
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One or more neighbouring
blocks
Varies between 125 to 600
dwellings
Area covered by one
enumerator
Full dissemination of
variables (subject to
confidentiality)
DISSEMINATION AREAS
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Area composed of one or
more neighbouring
blocks
400 to 700 persons
All of Canada
Problem: only available
from 2001 on
CENSUS TRACTS
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Somewhat larger area
that is relatively stable
Populations of 2,500 to
8,000
Located in large urban
centres only (50,000+)
Dissemination Areas for CT 004.00,
Prince George Census
Agglomeration
KEY CHALLENGES
(I) Are the small area units meaningful to your
research interests?
 (II) Small Area Estimates
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 Suppression due to confidentiality concerns
 Rounding (alternating up and down)
 Leads to greater margin of error in small area estimates
Unit
PROs
Block Face
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Enumeration Areas
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Dissemination Areas
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Census Tracts
very high resolution
 households and
entire country covered population counts only
fairly high resolution
 inconsistent boundaries
all Census questions
 higher risk of data
entire country covered suppression, influence of
rounding
consistent boundaries
fairly high resolution
all Census questions
entire country covered
consistent boundaries
 all Census questions
 lower risk of data
suppression
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CONs
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risk of data suppression
influence of rounding
lowest resolution
 potential for boundaries
to become “outdated”
 only available for larger
centres
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2011 & beyond – will data based on long-form
census be valid at small area level?????
“Long Form” census had been around a long time
(the 8 question short form was introduced in 1971)
 Sections:
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 Demography; Labour markets & income; Transportation;
Education; Language; Activity Limitations; Housing;
Citizenship and immigration; Ethnicity/culture
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Mandatory – fill it out or else fine or jail time!
One in five households (20% random sample)
2010 – Federal Government decided to cancel it
Replaced with a voluntary household survey
(National Household Survey)
Sampling error – three factors: size of population,
number of survey respondents, types of measures
used
 Larger # respondents lowers sampling error
 Stats Canada anticipates higher overall sampling
errors with move to NHS
 i.e., they are not expecting to collect data from
20% of households!
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Non-sampling error – e.g., respondent mistakes,
data collection mistakes, processing errors (but
these are constant)
 Biggest concern with a voluntary survey is nonresponse bias
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 Mandatory LFC had 96-98% responses, therefore non-
response bias fairly small
 Risk of non-response bias increases with decreasing
response rates
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Small area dissemination data most at risk from
decision to cancel the mandatory Long Form Census
 Voluntary surveys – uneven response rates, therefore both
sampling AND non-sampling error
 Increasing sample size does not resolve non-response bias
(only random sampling will)
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Canadian Centre for Policy Alternatives (no date) All the latest on the
Census long-form debacle.
http://www.policyalternatives.ca/newsroom/updates/all-latest-censuslong-form-debacle
Puderer, H, 2000, Introducing the Dissemination Area for the 2001 Census:
An update. Geography Division Working Paper Series, Catalogue no.
92F0138MPE. Ottawa: Statistics Canada.
Sheikh, MA, 2011, Good data and intelligent government. In A Gorbet
and A Sharpe (eds) New Directions for Public Policy in Canada: Papers in
Honour of Ian Stewart. Open access
http://www.csls.ca/festschrift/Sheikh.pdf