The purpose of the Post-Enumeration Survey is to measure the accuracy of the census. The survey measures the accuracy of the census by independently surveying a sample of the population.
The U.S. Census Bureau has used post-enumeration surveys with dual system estimation to measure coverage in the Decennial Censuses of Population and Housing since 1980. This approach involves case-by-case matching of people in an independent survey with people in the census to determine who was missed or counted in error.
The post-enumeration survey-based coverage measurement program associated with the 1980 Census was called the Post-Enumeration Program (PEP).
Starting with the 1950 Census of Population and Housing, the Census Bureau has followed a policy of carrying out a careful evaluation of each census's accuracy in terms of coverage, content, and procedures, together with research and experimentation.
The 1980 census had a research, evaluation, and experimental (REX) program consisting of over 40 separate projects that could be categorized in terms of their objectives as follows: