The 2006 Census counted 31,612,897 people in Canada during the national enumeration with reference day May 16, 2006. This count is lower than the published July 1, 2006 population estimate of 32,623,490 people. The difference between the two figures is not unexpected and is similar to that which was experienced in the 2001 Census. This note outlines why there are differences between census counts and population estimates.
The objective of a census is to provide detailed information at a single point in time on the demographic, social and economic conditions of the population. In this respect, one of its goals is to enumerate the entire population. Inevitably, however, some people are not counted, either because their household did not receive a census questionnaire (for example, if a structurally separate dwelling is not easily identifiable) or because they were not included in the questionnaire completed for the household (for example, the omission of a boarder or a lodger). Some people may also be missed because they have no usual residence and did not spend census night in any dwelling. In contrast, a small number of people may also be counted more than once (for example, a student living away from home may have been enumerated by his parents and by himself at his student address).
To determine how many individuals were missed or counted more than once, Statistics Canada conducts postcensal coverage studies of a representative sample of individuals. Results of these studies in combination with the census counts are used to produce current population estimates which take into account net undercoverage. In 2001, after these adjustments, the population estimate for Canada was 3.1% higher than the population enumerated in the census.
Postcensal coverage study results are usually available two (2) years after enumeration date. For the 2006 Census, preliminary postcensal study results will be released in March 2008. Final estimates of coverage error will be made available in September 2008. They will be used to revise and update the population estimates based on the 2006 Census results. Consequently, a series of revised population estimates for the period 2001 to 2008 will be disseminated in September 2008.
In studying trends in population growth between the 2001 and 2006 censuses, it is quite appropriate to compare census unadjusted counts from the two censuses. In most cases, the results will be similar to trends shown by the national and provincial population estimates, since the measurement of growth is affected very little by net undercoverage. The advantage of the census is that it provides a wealth of information on the population (language, ethnic origin, schooling and labour market activity) which is unavailable from any other source. The census also provides comparisons for small regions (below the census division level) for which demographic estimates are not available or are less precise.
On the other hand, population estimates provide a more accurate measure of population counts. Population estimates are the official figures used for counts of the Canadian population. In addition, they are utilized to measure the evolution of the population between censuses and provide explanations behind the population growth. They are available on a quarterly and annual basis at the national, provincial and territorial levels and are also available at the subprovincial level on an annual basis.