Wikipedia
Integrated Public Use Microdata Series (IPUMS) is the world's largest individual-level population database. IPUMS consists of microdata samples from United States (IPUMS-USA) and international (IPUMS-International) census records. The records are converted into a consistent format and made available to researchers through a web-based data dissemination system.
IPUMS is housed at the Minnesota Population Center, an interdisciplinary research center at the University of Minnesota, under the direction of Professor Steven Ruggles.
IPUMS draws on every surviving United States census from 1850 to 2000 (with the exception of 1890 census, which was destroyed in a fire) and from the American Community Survey since 2000 and the Current Population Survey since 1962. During certain years, IPUMS-USA also makes available over-samples of African-Americans, Alaskans, American Indians, Hawaiians, and Hispanics. The IPUMS provides consistent variable names, coding schemes, and documentation across all the samples, facilitating the analysis of long-term change.
IPUMS-International includes countries from Africa, Asia, Europe, and Latin America for 1960 forward. The database currently includes 159 samples from 55 countries around the world. IPUMS-International converts census microdata for multiple countries into a consistent format, allowing for comparisons across countries and time periods. Special efforts are made to simplify use of the data while losing no meaningful information. Comprehensive documentation is provided in a coherent form to facilitate comparative analyses of social and economic change.
Additional databases in the IPUMS family include: (1) the North Atlantic Population Project (NAPP), (2) the National Historical Geographic Information System (NHGIS), and (3) the Integrated Health Interview Series (IHIS).
The Journal of American History described the effort as "One of the great archival projects of the past two decades." The official motto of IPUMS is "use it for good, never for evil." All IPUMS data and documentation are available online free of charge.