From survey questions to demography
Cross-sectional population based surveys are widely used to collect demographic data. For example, see the Demographic and Health Surveys (www.measuredhs.com 
) which have collected nationally representative data from almost 100 countries since the 1980s. Surveys have large samples, usually around 1% of the population, and cover a wide range of topics including fertility and child survival. The surveys follow a standard core questionnaire an d there are many modules on specific topics that can be added to the core questions. Surveys are repeated at regular intervals to allow assesment of trends over time.
Repeated at regular intervals, surveys of this type provide detailed information on the demography at both national and sub-national level and can describe changes over time and differences by key characteristics.