The census long-form estimates come from a sample survey and are thus subject to sampling error and non-sampling error. The census short-form estimates come from a census and are thus only subject to non-sampling error.
Non-sampling errors include coverage, non-response, response and processing errors. They can happen during collection or processing operations, despite all efforts made to minimise them.
Sampling errors of long form estimates are measured with the standard error. The standard errors that are calculated and disseminated estimate the variability due to sampling as well as the variability due to total non-response of sampled households. Variability due to total non-response is taken into account because it can represent a significant portion of the total variability of the estimates since the sampling fraction is large.
One of the key data quality measures used for the Census of Population is the response rate. Table 10.1 in the Guide to the Census of Population, 2016 (http://www12.statcan.gc.ca/census-recensement/2016/ref/98-304/chap10-eng.cfm) shows the response rate for the 2016 Census of Population nationally, and for each province and territory. The rates are provided for the short-form and the long-form together, and for the long-form only.
Table 7 of the Income Reference Guide (http://www12.statcan.gc.ca/census-recensement/2016/ref/guides/004/98-500-x2016004-eng.cfm) provides the linkage rates to administrative sources nationally, and for each province and territory. The data quality section also has a description of the Income data quality indicator flags present in all the data products to show the amount of data not obtained from administrative sources for each geographic area. Separate data quality indicator flags are provided for products produced from the full census and those from the long-form sample estimates.