Comparability of the 2000 and 1990 Census Occupation Codes
Deane and Hyoung-jin Shin
November 19, 2002
This report documents procedures developed at the Mumford Center to compare the percent of the labor force in management, professional, and related occupations in 1990 and 2000. The comparability of occupational classifications across censuses is important for analyzing long-term trends in employment and other characteristics of workers. Unfortunately, Census 2000 uses different occupational codes than did the 1990 Census, and the changes had the net effect of counting more detailed occupations as management/professional. We cannot simply compare the percent of persons in this category in 2000 with the percent reported in 1990 without adjustments.
Census occupational codes in 1990 were based on the 1980 Standard Occupational Classification (1980 SOC) system that organized occupations into a hierarchical structure wherein knowledge, skill level, and the experience considered necessary for new entrants to an occupation determined an occupation's place in the classification system. In contrast, Census 2000 occupational codes are based on the 1998 Standard Occupational Classification (1998 SOC) coding structures in which occupations are grouped according to "job families." The general concept behind job families is to combine people who work together producing the same kinds of goods and services regardless of their skill level. For example, doctors, nurses, and health technicians are all members of a job family (SOC User Guide, 2001). This conceptual change makes it more difficult to identify the highly qualified occupations that were traditionally placed in the management/professional category at the top of the job hierarchy.
In addition to these changes in classification structure, the 1998 SOC has more professional, technical, and service occupations and fewer production and administrative support occupations than the 1980 SOC, reflecting advances in information technology, the shifts to a service-oriented economy, and increasing concern for the environment (BLS Report 929, 1999). Added and deleted occupations make it more complicated in many cases to know what occupation in one year is the equivalent of an occupation in the other year.
More complete information on metropolitan region occupational change between 1990 and 2000 is available on the Mumford Center web page: