“Population estimates” are different from the “Census population”. They are not directly comparable.
Census population is a count of the total number of people enumerated on the census day. It is often mistaken for the real or actual population. There is an average undercount of about 3% of the population, but this percentage is highly variable and typically higher in rural areas, First Nations, student residential areas and certain ethnic communities. On the Census day, some people were 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 border or a lodger). Some people may also be missed because they have no usual residence and did not spend census night in any dwelling. Some people did not respond, were traveling or forgot to respond. For example, students away from home, people out of the country at the time, people who do not fill in the survey for any reason, including lack of capacity or lack of official language skills, sick or infirm, part of a group that traditionally does not have a high fill rate (First Nations, temporary workers), etc. Some very small communities report a very high percentage of undercount. A few first nation reserves did not participate in Census 2016, for example, Six Nations, Chippewas and Oneida. The Census 2016 data for municipalities associated with these first nation reserves undercount the population.
Statistics Canada provides a partial explanation of undercount: https://www12.statcan.gc.ca/census-recensement/2011/ref/estima-eng.cfm. Furthermore, in https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1710000501 Statistics Canada shows that undercounts are adjusted for population estimates at Provincial and Canada levels. On this same page (add data if needed), note the 2nd quarter 2016 population estimate (36,109,487) for Canada, which is 957,759 and more people than the released population count (35,151,728) in the 2016 Census taken that quarter. This is a difference of 2.7%.
Statistics Canada conducts the Reverse Record Check (RRC) after Census to measure census population under-coverage and adjusts population estimates, e.g.,
http://www23.statcan.gc.ca/imdb/p2SV.pl?Function=getSurvey&SDDS=3902&Item_Id=47932
In “population estimates” we adjust the undercount of Census and estimate the actual population count. The foundation of our estimates is the current and historical Census in the five-year interval. We have developed an enhanced cohort survival model for population projection, which incorporates historical trends/census data, birth and mortality rates, migration and immigration, real estate development and settlement pattern. We also consider students and temporary workers as they are consumers in the communities where they reside. In addition, we consider the tax filer data, Alberta’s annual population count, new postal codes, housing startling statistics from Canadian Mortgage and Housing Corporation, immigration statistics and movers’ data. Our data reflects the current year population estimate is consistent with the estimate from Statistics Canada.