Codes and Frequencies
OCC1990 is a modified version of the 1990 Census Bureau occupational classification scheme. Like OCC1950, OCC1990 offers researchers a consistent long-term classification of occupations.
The occupational coding scheme in CPS data has changed several times since the 1960s. The CPS's occupational coding scheme has mirrored that of the Census Bureau, though the CPS has always introduced major coding changes one-to-three years later than the Census Bureau. All original occupational information is stored in the OCC variable. The meaning of codes in the OCC variable changes with each new coding scheme.
We chose the 1990 scheme as the standard for OCC1990 so that no year's occupational data would be forced to bridge both of the two most significant changes in census-based coding schemes: from 1970 to 1980 and from 1990 to 2000. In OCC1990, all samples from 1968 onwards bridge no more than one of these major shifts. For this reason, the variable may be preferable to OCC1950 for the samples from 1980 onward. Sensitivity testing suggests that OCC1990 performs very similarly to OCC1950 for most purposes.
The original 1990 occupational scheme has 514 categories. OCC1990 combines a number of occupational categories to maximize the variable's consistency over time. The resulting OCC1990 classification scheme contains 389 categories (see the "Codes and Frequencies" link above). Many users will want to further aggregate categories into the broad occupational categories implicit in the 1990 scheme: Managerial and Professional (000-200); Technical, Sales, and Administrative (201-400); Service (401-470); Farming, Forestry, and Fishing (471-500); Precision Production, Craft, and Repairers (501-700); Operatives and Laborers (701-900); Non-occupational responses (900-999).
OCC1990 was created using a series of technical papers published by the Census Bureau shortly after each census was administered. These papers provide detailed analyses of how the occupational coding scheme for each census year differed from the scheme used during the previous census year. These occupational "crosswalks" are based on samples of cases that are "double coded" into the occupational schemes of the current and previous census year. The original Census Bureau crosswalks are available via links in "Occupation and Industry Variables" of the IPUMS-USA documentation.
Using the information from the occupational crosswalks, we traced the proportion of each occupation as it broke out into more specific occupations or as it was combined with others into a more general occupation. To take one example from the technical paper produced after the 2000 census: of persons coded as "Gaming managers" in 2000 (2000 code 33), the Census Bureau determined that 35% would have been coded as "Managers, service organizations" in 1990 (1990 code 21), while 65% would have been coded as "Managers, food serving and lodging establishments" (1990 code 17). Thus, OCC1990 assigns a code of 17 to the cases in the 2000 IPUMS sample having an original 2000 OCC value of 33. We generated the same information for every occupational code in every census year from 1960-2000.
Researchers at the Bureau of Labor Statistics (BLS) then used the resulting tables to create aggregated occupational categories that were more useful for long-term analyses. We have performed a variety of tests to ensure that the new categories are as robust as possible over the long-term. More specifics on their methods and a detailed comparison of OCC1950 and OCC1990 can be found in the BLS Working Paper on the topic.
- 1968-1988: Civilians age 14+ who: were currently employed; or had previously worked and were looking for work; or were not currently in the labor force but had worked in the preceding 5 years.
- 1989-2018 2018: Civilians age 15+ who: were currently employed; or had previously worked and were looking for work; or were not currently in the labor force but had worked in the preceding 5 years.
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