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, as well as data from U.S. and international surveys. The records are converted into a consistent format and made available to researchers through a web-based data dissemination system.
IPUMS includes all persons enumerated in the United States Censuses from 1790 to 2010 (the 1890 census is missing because it was destroyed in a fire) and from the American Community Survey since 2000 and the Current Population Survey since 1962. 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 more than a billion individuals enumerated in 365 censuses from 94 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 the:
The Journal of American History described the effort as "One of the great archival projects of the past two decades." Liens Socio, the French portal for the social sciences, gave IPUMS the only "best site" designation that has gone to any non-French website, writing "IPUMS est un projet absolument extraordinaire...époustouflante [mind-blowing]!" 
The official motto of IPUMS is "use it for good, never for evil." All IPUMS data and documentation are available online free of charge.