MLP Version History
The version of the links available through the crosswalk files is sometimes newer than the version available via the IPUMS extract system due to the data processing and release cycle of the IPUMS USA project.
Version 1.2 (April 2024): The current version of the crosswalk data. This version differs from version 1.1 in using recently revised 19th century census files and adding more customization to the linking model to address changing variable availability across censuses. Additionally, this release provides links between 20 and 30-year census pairings as well as links to the 1950 census. We also provide crosswalks to the Social Security Numident data for the first time in this version in addition to World War II enlistment data linked to the 1940 census. The enlistment data were prepared by the CenSoc team at UC Berkeley. The version 1.2 links, including those for 1950, are not yet incorporated into the IPUMS extract system.
Version 1.1 (March 2023): The current version of the data available via the IPUMS extract system, also available as crosswalk files. This version differs from version 1.0 in using revised census files for some years. In addition, small changes were implemented in the linking code, including i) an updated name standardization file, and ii) census-specific inter-county and state distance files. The software that calculates name similarity was also updated, producing additional minor changes. These links are also available as crosswalk files.
Version 1.0 (September 2020): The original MLP data release, available only as crosswalk files. The first release included links for the 1900-1940 censuses. Crosswalks were added for 1850-1880 in September 2021, and for the twenty-year 1880-1900 census pairing in March 2022.
Linked Representative Samples: Between 2008 and 2010, IPUMS released linked representative samples (LRS) of the U.S. population spanning the period 1850 to 1930. These samples linked the full count 1880 database to the samples of the population from 1850, 1860, 1870, 1900, 1910, 1920 and 1930. Data and documentation are archived and available for analysis and replication. The LRS files are much smaller than MLP crosswalks, since linkages were from the 1880 full count census to 1% samples in other census years. The MLP linking strategy also differs from the LRS strategy.
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