What's new in IPUMS-98?

IPUMS-98 is a comprehensive revision of the Integrated Public Use Microdata Series. We have expanded the documentation threefold, added new datasets and variables, and revised dozens of variables.

New Documentation

In addition to the User's Guide, IPUMS-98 has two additional documentation volumes designed to make any reference to the original PUMS codebooks unnecessary. The User's Guide Supplement (Vol. 2) contains geographic tools such as maps, tables of historical changes in metropolitan area composition, descriptions of data allocation procedures, and detailed supplementary variable information. Volume 3, Counting the Past, has all enumerator instructions, copies of enumeration forms, capsule histories of the censuses, and descriptions of PUMS sample creation procedures. Two further volumes detailing how original PUMS variables were assigned IPUMS values are in preparation. We will make on-line hypertext versions of the documentation available soon.

New Datasets

New Variables

Because of the additional variables, we were forced to revise the layout of the raw data files. This will not affect users of our automated data extraction system.

Revised Variables

In addition, we developed more consistent classifications of missing, "not applicable," and "not specified" categories. Wherever it was possible to impose a consistent universe without losing information, we did so.

Data Quality Flags

We have added a number of data quality flags previously excluded, made new flags corresponding to IPUMS allocation procedures, and corrected errors in flag coding and record layout.

Missing Data Allocation

We have allocated missing and illegible cases for all substantive variables from 1850 to 1920. Corresponding data quality flags are constructed to indicate where the data have been changed. In addition to the variables allocated in IPUMS-95, missing cases have been allocated for county, urban status, city, city population, metropolitan area, farm, ownership, mortgage, duration of marriage, children ever born, children surviving, citizenship, year naturalized, year immigrated, years in U.S., mother tongue, language, school, literacy, employment status, occupation, industry, class of worker, period unemployed, age in months, and month of birth.

Error Correction

We have made many corrections to the data since IPUMS-95 not documented above. Some were errors of the original census samples; others were introduced in the creation of IPUMS-95. We appreciate the help of those researchers who helped us identify a number of these data problems.

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