Summary
Population data can be gathered from a number of sources. This session has outlined the primary sources, their advantages and disadvantages, and outlined some options for when data from these sources are not available.
Censuses are the main source of data on population stock. Ideally held every ten years, they involve an enumeration of the entire population of a nation and often include the collection of additional information on social and economic characteristics. However, censuses can only provide a “snapshot” of a moment in time, and by the time all the data has been collated, analysed and disseminated, it will often be a number of years out of data. Furthermore, censuses are expensive, time-consuming and require large amounts of man-power. Because of these disadvantages, a number of countries have moved towards population registers. These collate and link information from vital registration and administrative registers, and provide an up-to-date and near instantaneous profile of the population.
Vital registration – the registering of vital events, such as births, deaths and marriages – remains the ideal source of information on demographic events. However, many countries in the world do not have a high quality system for vital registration, if they have a system at all. In these situations it may be possible to use alternative methods to estimate the number of demographic events, such as sample registration, demographic surveillance sites and verbal autopsy. Nevertheless, these should be seen as interim measures, with a comprehensive system of vital registration still seen as the ultimate goal.