Steve Ruggles and the IPUMS staff at the University of Minnesota have prepared the following description (modified for changes in the Web site):
The Integrated Public Use Microdata Sample (IPUMS), created at the Social History Research Laboratory of the University of Minnesota, is now available. The IPUMS consists of multiple samples of the U.S. Census. Together they comprise our richest source of quantitative information on long-term changes in the American population. The IPUMS combines these high-precision samples of the U.S. population into a single database spanning 1850 to the present.
Most of the census samples have existed for several years, but because the original samples were coded and formatted differently, they have been very difficult to use in combination. The IPUMS assigns uniform codes across census years and integrates the documentation into a coherent form.
A preliminary version of the IPUMS was released in Fall 1993. The current release contains virtually all variables available in all census years, as well as a consistent set of constructed variables to enhance ease of use. Samples from every available census year are included in the current IPUMS.
The IPUMS database is accompanied by a User Guide which can be downloaded with the data.
IPUMS staff can be reached via the "Contact Us" links
on their
usa.ipums.org/usa/
and
www.ipums.umn.edu/international/
Web pages.