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 2006 Census results.