After a 72-year wait required by law, the National Archives has released individual records from the 1940 Census, opening a gold mine for people researching their family histories. But the 1940 Census also played a notable role in the history of census-taking: It helped usher in the modern era of sample surveys.
With the nation deep in the Great Depression, government officials planning for the 1940 Census hoped to expand the topics they asked about in order to guide federal policy-making in an era of expanded government. They wanted to add questions to the census about people’s incomes, migration histories and housing conditions.
But adding these new questions would have made the census form too lengthy, and been too costly. After lobbying by some of its younger statisticians, the Census Bureau’s solution was to turn to the new science of survey sampling. To make room for new topics, the Census Bureau decided for the first time to ask some questions of a sample of respondents, not of everyone. Those responses were extrapolated to the total population.
Read the full report, Sample Surveys and the 1940 Census, on the Pew Social & Demographic Trends website.