By David Van Riper, Etienne Breton, and Sarah Flood
Have you ever wanted to link external city-level data to CPS respondents but were stymied by the city coding system used by the CPS? With the release of two new variables (PLACECENSUS and PLACEFIPS), IPUMS CPS has simplified the task of making such linkages.
The CPS identifies a limited number of sub-state geographic units (e.g., cities, counties) because of the complex assignment of CPS geographic identifiers (see working paper) and required minimum population thresholds. An additional layer of complexity is a custom coding scheme for central/principal cities (INDIVIDCC) that is unique to the CPS and, therefore, unfamiliar to most data users. IPUMS CPS has addressed this issue through the creation of two new variables – PLACECENSUS and PLACEFIPS – which provide standard codes for identifying central cities. These new variables will dramatically simplify the process of using IPUMS CPS to study specific cities, and will be particularly beneficial to those who want to augment the CPS data with city-level characteristics.
While metropolitan areas have almost always been identified in CPS (see METFIPS), central or principal cities – defined as the largest or one of the largest cities in metropolitan areas – were not identified in the data until October of 1985 (see INDIVIDCC). The identification of cities is great for users – they can focus their analyses on these cities (paying close attention to sample size and applying weights of course!). If analyses are confined to the CPS only, INDIVIDCC is adequate for use. However, attaching city-level characteristics to CPS data quickly becomes a problem given the native coding scheme for INDIVIDCC that is not used in other data products.
The new IPUMS CPS variables PLACECENSUS and PLACEFIPS help mitigate the challenge associated with augmenting city-level data from other sources with CPS data.
- PLACECENSUS (available October 1985 to May 1995) uses Census city codes developed by the Census Bureau. The Census Bureau developed standard Census codes for cities that they applied to the 1970 and 1980 decennial censuses. The codes are assigned to each place in alphabetical order within a state.
- PLACEFIPS (available September 1995 forward) uses FIPS codes. were developed by the National Institute of Standards and Technology (NIST) in the 1980s and have been used by the Census Bureau for decennial censuses since 1990 and in many other datasets published by the United States government (e.g., American Community Survey). FIPS codes are assigned to each place in alphabetical order within a state.
- Neither PLACECENSUS nor PLACEFIPS are available for the June to August 1995 data. During this period, there are no sub-state geographic identifiers in the data.
- PLACECENSUS and PLACEFIPS codes are unique within states, so users must combine the PLACECENSUS or PLACEFIPS codes with a state identifier (STATEFIP or STATECENSUS) to uniquely identify each central city.
