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8.  Sample estimate and population count consistency

8.1  Dissemination areas
8.2  Weighting areas
8.3  Census subdivisions
8.4  Census tracts
8.5  Census divisions

In Chapter 7 (see Table 7.2.2.1), the discrepancies at the Canada level between the population counts and corresponding sample estimates based on final weights were studied where

An equation to calculate the population/estimate discrepancy

The comparison between sample estimates and population counts is based on occupied private dwellings from sampled CUs.

In this chapter, these population/estimate discrepancies from both the 2001 and 2006 censuses will be examined for the following geographic levels:

(a) dissemination areas (DAs);

(b) weighting areas (WAs);

(c) census subdivisions (CSDs);

(d) census tracts (CTs);

(e) census divisions (CDs).

At the WA level, we observe that zero population/estimate discrepancies are guaranteed for constraints that are retained by the weighting system. In general, geographic areas made up of whole WAs have small population/estimate discrepancies. Table 7.1.2 reveals that 13.2% of CSDs and 67.0% of CTs consist of one or more whole WAs. In addition, because of the way in which WAs are formed, 100% of CDs consist of whole WAs.

The charts and tables in this chapter provide the percentiles of the population/estimate discrepancies for 33 characteristics which, except in a few cases, are identical to the 34 WA-level constraints applied to the census weights (see Appendix B). Let us define the term 'percentile' by way of an example. For instance, Table 8.2.1 shows a 10th percentile of -11.12% for '6+-person households' in 2006. This means that 10% of the WAs have discrepancies of -11.12% or less. A 90th percentile of 6.75% means that 10% of the WAs have discrepancies of 6.75% or more. Population/estimate discrepancies for geographic areas having a population count less than or equal to 50 for a given characteristic are excluded from the tables and charts in this chapter. These discrepancies were found to be relatively large and could have significantly altered the percentiles presented in this chapter.

In the next few sections, the 2006 discrepancies will be compared to those in 2001 for various levels of geography.

8.1  Dissemination areas

Canada is divided into 54,626 DAs, of which 52,448 contained sampled households in the 6,602 WAs in the weighting process. A DA, on average, will have a population of 580 persons.

In comparing Charts 8.1.1 and 8.1.2 to the other charts in this chapter, it is obvious that the population/estimate discrepancies are somewhat higher at the DA level than at the WA, CSD, CT or CD levels. This is not surprising given that WAs are made up of whole DAs and that WAs are the lowest level at which sample estimates will agree with population counts for most characteristics.

For the most part, the distribution of the discrepancies at the DA level is similar in 2006 compared to 2001 with them sometimes being slightly larger and sometimes being slightly smaller. The discrepancies are marginally higher, however, for most age range constraints in 2006 compared to 2001.

8.2  Weighting areas

Canada is divided into 6,607 WAs, of which 6,602 are sampled WAs. On average, each WA has a population of 4,785 persons and is composed of 8 whole DAs. WAs are used for calculating census weights but no results are published at this level.

Table 8.2.1 shows that, for both the 2006 and 2001 censuses, the 10th, 25th, 50th, 75th and 90th percentiles are zero for all person characteristics. For the household characteristics, most of the 25th, 50th, and 75th percentiles are also zero, while some of the 10th and 90th percentiles are non-zero. These results are not surprising given that WAs consist of the lowest level at which sample estimates are forced to agree with population counts for the weighting constraints. The most noticeable difference is the larger discrepancies for the 5-person and 6+-person households, which is to be expected based on the Canada level discrepancy for these constraints. The two dwelling type constraints have non-zero percentiles at the WA level because controlling on them was parameterized and not included in every WA

8.3  Census subdivisions

Canada is divided into 5,418 CSDs. CSDs correspond to municipalities or to areas deemed to be equivalent to municipalities for the purposes of statistical reporting (e.g., an Indian reserve). They have an average population of 5,859 persons, but can range anywhere in size from a very small town to a very large city. Table 7.1.2 shows that 13.2% of CSDs consist of one or more whole WAs.

Charts 8.3.1 and 8.3.2 summarize the population/estimate discrepancies for all sampled CSDs in Canada. For the most part, the distribution of the discrepancies at the CSD level is similar in 2006 compared to 2001. The discrepancies are marginally higher, however, for age range constraints for the 10th, and 90th percentiles in 2006 compared to 2001. The trend does not hold for the 25th and 75th percentiles of the age range constraints. There are also some large discrepancies in 2006 for the 5-person and 6+-person households. This is not surprising given the large discrepancies, based on the initial weights, seen in Chart 6.1.

8.4  Census tracts

CTs are only located in large urban centres having an urban core population of 50,000 or more. There are 5,089 CTs in Canada. CTs usually have a population ranging from 1,500 to 8,000 persons, with the average being approximately 4,500 persons. Table 7.1.2 shows that 67.0% of CTs consist of one or more whole WAs.

Chart 8.4.1 summarizes the population/estimate discrepancies for all sampled CTs in Canada. It is not surprising that the discrepancies are similar between 2001 and 2006 for most characteristics. Just like with the CSDs, the 5-person and 6+-person households have large discrepancies at the 10th and 90th percentiles.

8.5  Census divisions

Canada is divided into 288 CDs. CDs have an average population of approximately 110,000 persons.
A CD might correspond to a county, regional municipality, regional district, or any other area established by provincial or territorial law.

Table 8.5.1 summarizes the 2006 and 2001 Census population/estimate discrepancies for the sampled CDs. All CDs consist of complete WAs. Thus, characteristics that were rarely discarded have perfect or nearly perfect consistency at the CD level. With the exception of the 5-person and 6+ person household characteristics, the size of discrepancies for characteristics that were discarded more frequently is still very small.

Chart 8.1.1  Percentiles of population/estimate discrepancies for 2006 and 2001 dissemination areas (age characteristics)

Chart 8.1.2  Percentiles of population/estimate discrepancies for 2006 and 2001 dissemination areas (non-age characteristics)

Table 8.2.1  Percentiles of population/estimate discrepancies for weighting areas

Chart 8.3.1  Percentiles of population/estimate discrepancies for census subdivisions (age characteristics)

Chart 8.3.2  Percentiles of population/estimate discrepancies for census subdivisions (non-age characteristics)

Chart 8.4.1  Percentiles of population/estimate discrepancies for census tracts

Table 8.5.1  Percentiles of population/estimate discrepancies for census divisions

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