Topics for population censuses
The selection of census topics should be based on the output expected to be produced by the census. Thus, at the beginning of the process of selecting topics stands a clear identification of expected outputs. A number of considerations have to be taken into account when deciding which topics should be covered in the census. Firstly, prime importance should be given to the fact that population censuses should be designed to meet national needs. Secondly, census topics should be selected in a way that ensures a high comparability of results both internationally and over time. Thirdly, it is important to select only topics for which the respondents will be willing and able to provide adequate information (and avoid those which may arouse fear, local prejudice or superstition). Finally, the selection of topics should be carefully considered in relation to the total resources available for the census (see the “Principles and Recommendations” for more detailed discussion of this issue).
The “Principles and Recommendations for Population and Housing Censuses, Revision 2” provides a list of topics to be investigated in population censuses of recommended topics. It distinguishes between “core topics” collected directly, “derived core topics” and “additional topics”. Although derived core topics are based on information in the questionnaire, they usually – but not exclusively – do not come from replies to a specific question but are rather obtained indirectly (e.g. total population). Additional topics are such topics which are not regarded to have the highest priority but which some countries may find useful to include in their census.
As part of the 2010 World Programme on Population and Housing Censuses the UNSD is analyzing questionnaires used in population censuses according to the topics covered in the questions. The document Implementation of population census topics in the 2010 census round shows for every topic the number of countries which asked questions concerning this topic. This is done only for the direct core topics and the additional topics, since derived topics can usually not be linked immediately to questions in the questionnaire. The results are rather minimum counts and should be interpreted with caution since not all topics are based on information coming from the personal questionnaire. Some information is asked directly in the questionnaires but may also come from other enumeration material or a combination of them; this is in particular true for some topics concerning geographical characteristics such as “place of usual residence” or “place where present at time of census”. Furthermore, some topics may be covered by combining information from different parts of the questionnaire (for example, the “age of mother at birth of first child” can be asked for directly or can be calculated by subtracting the date of birth of the women from the date of birth of the first child born).The document Countries and the number of population census topics covered in their census questionnaires (2010 census round) shows the different degrees to which countries covered population topics in their census questionnaires. The same considerations given above apply also for the interpretation of this table. Furthermore, it has to be considered that some countries, in particular those with the most developed statistical systems, are relying for information on a number of topics on non‑census sources. Those countries may show only a low number of topics covered in their census questionnaire although data on this topic is available from other sources including population and other registers, and also sample surveys.