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    The Integrated Public Use Microdata Series (IPUMS-USA) is an online, openly accessible resource of more than fifty samples of the American population drawn from fifteen federal censuses and from the American Community Surveys of 2000-present. IPUMS-USA is composed of microdata and includes a data extraction system that enables users to select the samples and variables they require. 

    Apr 14, 2017 5:09pm
    Subject Areas
    Collection Content

    IPUMS USA collects, preserves, and harmonizes U.S. census microdata and provides access to data with documentation. Data includes decennial censuses from 1790 to 2010 and American Community Surveys (ACS) from 2000 to the present. IPUMS assigns uniform codes across all of the samples and bring relevant documentation into a coherent form to facilitate analysis of social and economic change. The census microdata are composed of individual records containing information collected on persons and households. 

    The IPUMS samples consist of records of two types: household and person records. Each household record is followed in the raw data files by a series of person records, containing information about each sampled individual in the unit. The data includes information on a broad range of population characteristics including: fertility, nuptiality, life-course transitions, immigration, internal migration, labor-force participation, occupational structure, education, ethnicity, and household composition. Generally the later census years provide a wider range of characteristics while the earlier years often contain greater detail for the available variables. 


    Users access data through the IPUMS USA online data extraction system. The system enables users to select a subset of cases and variables for analysis and creates a record layout tailored to the needs of each user. 

    IPUMS documentation is organized into five volumes; Volume I covers overall design of the database, variable descriptions, and coding schemes for each variable; Volume II includes supplemental information on more complicated variables such as maps and geographic area coding schemes and alternate occupation and industry coding schemes available for a particular census years; Volumes III provides enumerator instructions and replicas of the census forms, procedural histories of the censuses, descriptions of missing-data allocation procedures and other post-enumeration processing; and finally, Volumes IV and V consist of complete descriptions of all the data transformations carried out by IPUMS. 

    Most analyses of IPUMS data require manipulation of both household and person records; each record contains a serial number which links the persons in the housing unit to the appropriate household record. Users will specify which statistical software formats (e.g. SPSS, STATA, or SAS) they would like the command files to be generated as when extracting data.


    Access to the IPUMS documentation is freely available online, without restriction. However, users must register with IPUMS before extracting data from the website.

    Strengths and Weaknesses

    For the period since 1950, census microdata are subject to confidentiality measures that limit their usefulness; the IPUMS samples for these years include no names, addresses, or other potentially identifying information. Additionally, the Census Bureau limits detail on place of residence, place of work, very high incomes and several other variables to ensure that no individuals can be identified. The microdata records for periods since 1950 identify no geographic areas with fewer than 100,000 inhabitants (or 250,000 in 1960 and 1970) and is therefore inappropriate for research that requires identification of specific small geographic areas. 

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