The Census questionnaire items aimed at capturing the age of each person in a household have changed from census to census.
Age is determined in completed years as at the time of the census.
Studies indicate that counts in 1970 and 1980 for persons 100 years old and over were substantially overstated. For 1990, persons aged less than 1 year were likely to have been reported as being 1 year since the alternative was 0 years. It is likely that approximately 10 percent of persons in most age groups are actually 1 year younger than reported due to the tendency of respondents to round up to the next age.