The Relationship Between The 1990 Census and ... - Census Bureau

After 1990, however, the crosswalks provided in this paper became necessary even more than in previous
censuses, because for the first time both the standard industry and occupation classifications underwent
major revisions in the same decade. The 1987 Standard Industrial Classification (SIC) was replaced in
1997 by the North American Industrial Classification System (NAICS), and the 1980 Standard
Occupational Classification (SOC) was replaced in 1998 by a completely revamped SOC. The 1998 SOC
then evolved into a slightly modified update in 2000. The 1997 NAICS and 2000 SOC, respectively,
provided the structure for the Census 2000 Industry and Occupation Classifications. The major
differences between the 1997 NAICS and 2000 SOC and their previous counterparts became equally
major differences between the 1990 Census and Census 2000 classifications. When data users look at
census data from 1990 to 2000, therefore, they are faced with apparent changes in the industrial and
occupational distributions of the workforce that are due more to classification revisions than to real
changes in the workforce itself. Data users need ways to sort out the classification revisions from the real
changes. The crosswalks provide them with the means to do so.
REVISIONS TO THE INDUSTRIAL CLASSIFICATION
As mentioned above, the Census 2000 industrial classification system was based on the structure of the
1997 NAICS. The NAICS replaced the previously used SIC because rapid changes in the U.S. and world
economies brought the SIC under increasing criticism. In July 1992, the Office of Management and
Budget (OMB) established the Economic Classification Policy Committee (ECPC), and charged it with a
“fresh slate” examination of economic classifications for statistical purposes. The ECPC ultimately joined
with representatives from Mexico and Canada to develop the NAICS.
The NAICS provides common industry definitions and replaces the previous industrial classifications for
all three North American countries. It groups establishments into industries based on the activities in
which they are primarily engaged. It is a comprehensive system covering the entire field of economic
activities, producing and non-producing. Two classification principles that had the most impact on the
differences between the SIC and NAICS are as follows 2 :
1. NAICS was erected on a production-oriented or supply-based conceptual framework. This means
that producing units that use identical or similar production processes are grouped together in the
NAICS.
2. The system gives special attention to developing production-oriented classifications for (a) new
and emerging industries, (b) service industries in general, and (c) industries engaged in the
production of advanced technologies.
The resulting NAICS arranged industries into 20 sectors, compared to 10 divisions used by the 1987 SIC,
and 1,170 detailed categories for the United States. The Census Bureau then aggregated these detailed
NAICS categories into 265 detailed census categories within the same 20-sector framework of the
NAICS.
Systems in Terms of Their 1960 Occupation and Industry Elements (issued July 1972); and Technical Paper 18: Changes
Between the 1950 and 1960 Occupation and Industry Classification (issued 1968).
2 See Bernan Press: North American Industry Classification System, United States, 1997 (published 1998).
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