"A microdata file is the set of answers obtained by survey path. For household surveys or population censuses, files of this type are hierarchical if the data on all the persons in the households sampled or enumerated are present. The statistical agencies ensure that this data remain anonymous by eliminating all possibility of identification. A number of countries produce hierarchical files of microdata from their censuses. Canada, however, does not. As a matter of fact, Canada has disseminated microdata files since 1971 but these files have always been designed without incorporating the complete hierarchy of households. We are assessing here the protection of statistical confidentiality for the 2001 census, that is, we are assessing whether it is easy or very difficult to identify individuals from data alone. We define two measurements of statistical confidentiality protection: the conditional probability of uniqueness and the conditional probability of exact matches. We apply these two measurements to a set of records from the 1996 census for various groups of variables. On the basis of the results obtained, we conclude that publication of a public use hierarchical file significantly reduces the protection of statistical confidentiality"--Abstract, p. iii.