Almost all countries in the world conduct a population and housing census at least every ten years, to produce key data for planning and administration at national and local level. In recent decades, census methodology and technology has developed significantly. Countries in the UNECE region are leading this change, which aims at limiting costs, reducing burden on respondents, improving quality, and increasing the frequency of census results.
Traditionally, a census is conducted by a full field enumeration, which means that census questionnaires are filled for each person and each dwelling in the country. This method is complex and expensive, and requires that the population cooperates. However, in many countries, an increasing number of persons are more difficult to find at home, for instance because they move frequently between various residences, or refuse to participate in the census.
Already in the 1970s, the Nordic countries started developing their administrative registers (including population, buildings and business registers) to be able to link data across registers and produce census results without collecting any additional information (the so-called “register-based census”). In the course of the 1990s, other European countries developed new methods, also in response to the decreasing participation of the respondents. The “combined census” was developed, where some data is taken from registers and combined with other data obtained from a limited field collection. The use of data from administrative registers makes the census more efficient, because producing statistics from existing registers – once the register-based statistical system is in place – is much less expensive than collecting data from the population.
Another alternative method is the “rolling census” developed in France. With this method, every year there is a limited data collection, and the data across years are aggregated to produce estimates that are updated regularly. The advantage compared to the traditional census is that the large amount of work and the costs of field data collection are spread over time.
In the 2010 census round, the trend of adopting alternative census methods has accelerated in the UNECE region: 19 countries (mostly EU and EFTA members) conducted a register-based or combined census, compared to only 8 in the previous (2000) census round. And for the next (2020) census round the number is expected to increase further to at least 26, so that about half of the UNECE countries will adopt an alternative census method (figure 1).
