The article analyzes how differences in Canadian and American linguistic ideologies affect the tasks of population censuses, the wording of language questions, and the information extracted from the census sheets. The Canadian ideology of multiculturalism and the preservation of linguistic diversity, unlike the American ideology of the “melting pot”, is characterized by great attention to the use of official languages, indigenous languages and immigrant languages, which is reflected in the inclusion of detailed questions about the inventory of languages and respondents' language competencies. Processing data from the census allows Canadian socio-linguists to form a significant number of language indicators describing various aspects of Canadian institutional bilingualism and multilingualism, monitor compliance with the rights of speakers of different categories of languages, and predict changes in the language situation in the country. The relative decrease in the share of speakers of official languages (Engl