Linked Census Data Extracts
— MLP version 2.0: released July 2025 —
The IPUMS dissemination system produces custom data files composed of individuals linked across censuses by the IPUMS Multigenerational Longitudinal Panel project (MLP). The linked data are accessed via the "USA Linked Censuses" tab on the Select Samples screen. Selecting the checkbox for "use linked censuses" enables the screen and constrains your choice of censuses to the full-count datasets only. Any other datasets in your data cart will be dropped and cannot subsequently be added unless you uncheck the box or clear your data cart to leave linked-census mode.
The grid of buttons on the linked census screen displays all available census combinations from 1850 to 1950. The number on each button indicates the linked case count in millions for each census combination. Census links longer than 80 years are not offered. Select any number of buttons to indicate the linked cases you want to include in your extract. The system will create a single extract containing all the selections that you indicate. Selections are additive: choosing the buttons for 1850 to 1860 and 1900 to 1920 will yield an extract containing all cases that link between 1850 and 1860 AND all cases that link between 1900 and 1920. Note that no 1910 cases will be included in your extract unless you explicitly choose sample combinations that include that year. For example, if you want every link that occurs between 1900 and 1920, you would select 1900-1910, 1900-1920, 1910-1920.
Once you have made your selections, hit the submit button and proceed to select variables to include in your extract. Some variables related to linking are automatically added to your data cart, including the Historical Identification Key (HIK) variable that uniquely identifies persons across all census years. Linked extracts, like all full count extracts, can be large. Be as parsimonious as possible when selecting variables and census combinations to include in a single extract.
Extract format. The linked data extract will be produced in standard IPUMS format: all the person records for census year X followed by all person records for census year Y, etc. Users may use HIKs to sort this into a long file for analysis, reshape the data to a wide file, or otherwise manipulate the data as appropriate for their application.
Non-linked household members. By default, only linked cases will be included in your data extract. There is a radio choice on the linked census screen that allows you to also include everyone who resided with the linked person. The choice to include non-linked household members will result in a more complicated dataset for analysis while providing more contextual information for the linked persons.
Case selection warning. Users should be very cautious about using case selection with linked extracts. Performing case selection on time-variant characteristics — such as age, marital status, or state of residence — risks excluding some observations for a person. For example, no person is age 10-15 in more than one census, and imposing that case selection will yield an empty dataset. Only variables that should not vary over time (e.g., birth year, birthplace, sex) are good candidates for case selection. But because of noise in the source data, even these variables are not entirely reliable over time.
IPUMS MLP Project. The census links were created by the IPUMS Multigenerational Longitudinal Panel (MLP) project. Roughly 40 to 50 percent of individuals are linked between adjacent censuses, with fewer links over longer timespans. More information about the MLP project and the construction of the census links is available here.
Citation and terms of use
Cite both IPUMS MLP and the Full Count IPUMS Ancestry data:
Steven Ruggles, Nesile Ozder, Catherine A. Fitch, Matthew Sobek, Julia A. Rivera Drew, J. David Hacker, Jonas Helgertz, Cheyenne Lonobile, Matt A. Nelson, Evan Roberts, and John Robert Warren. IPUMS Multigenerational Longitudinal Panel: Version 2.0 [dataset]. Minneapolis, MN: IPUMS, 2025. https://doi.org/10.18128/D016.V2.0
Steven Ruggles, Matt A. Nelson, Matthew Sobek, Catherine A. Fitch, Ronald Goeken, J. David Hacker, Evan Roberts, and J. Robert Warren. IPUMS Ancestry Full Count Data: Version 4.0 [dataset]. Minneapolis, MN: IPUMS, 2024. https://doi.org/10.18128/D014.V4.0
Publications and research reports making use of IPUMS should be added to our Bibliography.
Contact us
For questions about IPUMS MLP, contact ipums@umn.edu.
Supported By
