National censuses vary from country to country in the priority given to national enumeration, in the type and level of data they contain, in geographical coverage, in the terminology and methodologies used, in how the data is presented, and in how often they are conducted, if at all. As a result, census publications are sometimes difficult to find and to use.

National censuses are collected, published and disseminated primarily by each country's census or national statistical office (NSO) or its equivalent. Census data are published in each country's vernacular, and as appropriate, many offer English as well as other language versions. Statistical offices of international agencies (e.g. United Nations, statistical organizations for member states like the ASEAN, Eurostat, and OECD), also publish statistical data including population figures. The most consistent data in terms of format and frequency, whether online or in print are usually generated from them.

Current estimates and projection figures update official census year data. These data are readily available in the current statistics sections of electronic resources, in serials that update printed publications, and are usually the reference figures found in statistical compendia.

Electronic resources provide quick access to current and some historical data. Among the better sites for international census data are those maintained by the census or NSOs of each country, by international organizations, by research organizations, or by university library research centers. These sites usually contain a combination of resources, links to data sites, and actual census data. When researching international census data online, expect differences in data access, i.e., what's free, fee-based, browse only, downloadable, etc. Have patience when maneuvering through a statistical web site because it may take several links to obtain the data you want.

Please see the U.S. Census Connections: A Resource Guide if you are interested in the U.S. census data. Send your questions related to finding census data to Ask a Librarian.