Population data provide an invaluable reference for policy formulation, academic research and business decision-making. Such data have to be collected through population census. A population census is a complete count of the population, i.e. a complete enumeration, which is conducted once every ten years due to the huge resources required. However, with the rapid development of the society, it is inadequate to update population data only once in ten years. Therefore, according to international practice, a population by-census, which is a large-scale household sample survey, is conducted in between two censuses to collect information on individuals living in a sample of housing units. Data collected are used to extrapolate the size and characteristics of the entire population using statistical methods and also serve as benchmark for revising population estimates for the past five years and preparing population projections for future years.
The third round of population by-census will be carried out in 2016, with the previous two rounds being conducted in 1996 and 2006 respectively. Along with social development and in response to the needs of data users, information collected from population by-censuses have been adjusted accordingly. For instance, the 2006 By-census collected additional data on resident participation in leisure activities; the 2011 Census collected more detailed information on higher education attainment, etc. In the 2016 Population By-census, questions on job changes, self-care ability of individuals aged 60 and above, etc. will be added.