Emerging methodologies for population censuses and implications on comparability of census data: selected results from the 2000 census round and perspectives for the 2010 round

The population census represents one of the "pillars" of national statistical systems, since it provides the benchmark for population counting and represents a major (in some countries the only) data source on the main characteristics of the population at the national and local level.

Traditionally, the population census was conducted by counting all individuals and collecting information on their characteristics using census paper questionnaires. This approach requires a huge amount of financial, human, and organisational resources. Given the complexity and the costs of the operation, for most countries conducting a successful census is a challenge. Many countries are increasingly facing pressure to reduce census costs, spread them over time, use available information whenever possible, produce data more frequently, and cover new emerging topics. This has caused many countries, particularly in Europe and North America, to consider alternatives to the traditional census methodology.

Already in the 1970s, several Nordic countries started shifting towards censuses based on administrative registers. In the last years, an increasing number of countries moved away from the traditional census. Innovative methods have been developed, including the use of register data in combination with results from ad-hoc or existing surveys, or the French "rolling census". For the 2010 census round, it is expected that almost half of the countries in the UNECE region (covering Europe, North America and the Commonwealth of Independent States - CIS) will adopt a non-traditional census methodology, in most cases making use of data from administrative registers.

The adoption of different census methodologies can potentially have an impact on the comparability of census data across countries and - within countries - across time. In this regard, a key role is played by the international recommendations. For the 2010 census round, UNECE and Eurostat prepared the Conference of European Statisticians Recommendations for the 2010 Censuses of Population and Housing, which represents the main statistical standard used in the UNECE region. The CES census recommendations are intended to improve the comparability of census data through the selection of a core set of census topics and the harmonization of definitions and classifications. Compared to similar sets of recommendations prepared for the previous census rounds, special attention was paid to the fact that an increasing number of countries are expected to adopt emerging census methodologies and technologies for the next census.

In the framework of the preparation of the CES census recommendations, the UNECE collected from member countries information on practices followed in the censuses of the 2000 round and on plans for the 2010 census round. Based on this information, it is possible to assess the comparability of the census data for selected topics and try to estimate the potential impact of the adoption of emerging census methodologies.