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

would have been assigned to an “unexpected” 1990 category if the title had existed in the 1990
index. 5
3. The 2000 occupation index was affected by changes to the 2000 industry classification that
occurred, in turn, as a result of the new NAICS. Many occupational titles can go to different
occupation categories, depending on the industry in which that occupation is found. For example,
a “chaser” in the logging industry goes to a different occupation category (“logging workers”) than
a “chaser” in a finance company (the category for “bill and account collectors”). The assignment
of these titles from the index depends, therefore, on what the Census Bureau calls “industry
restrictions” provided for each line in the index. Changes to these industry restrictions caused by
changes in the NAICS had subtle effects on the distributions between 1990 and 2000 occupation
categories that are not always reflected in the occupation index crosswalks.
In addition to showing the number of lines in the indexes going from one category to another, the index
crosswalks also computed the expected percentage of each 1990 category going to each 2000 category.
These distributions of numbers and percentages provided information that helped determine the accuracy
of the double-coding of the sample of 1990 industry and occupation responses, as described below.
Double-coded 1990 Census Sample
The 1990 Census Sample used for this project was selected so that it would contain at least 200 records
for each 1990 3-digit industry and occupation code assigned to the “experienced civilian labor force
(ECLF).” The experienced civilian labor force, for purposes of this analysis, consists of all non-military
individuals who were either employed or unemployed at the time of the census enumeration, and who
provided a description of their current job, or (if unemployed) their most recent job held in the 5 years
prior to the census.
Some small occupation categories had fewer than 200 people coded nationwide, so all records for those
codes were taken. Each individual code, therefore, had a sample that represented all the people in the
ECLF assigned to that code in the 1990 census. The entire sample contained 146,686 records, of which
48,784 were used for the analysis of the industry classifications, and 97,902 were used for analyzing the
occupation classifications.
Each record contained the industry and occupation codes originally assigned in the 1990 Census. Over the
next 10 years, all the records in sample were re-coded several times, still using the 1990 classifications, by
the Census Bureau’s current survey coders and Census 2000 coders in its Jeffersonville, Indiana
Processing Office (the National Processing Center, or NPC), and by staff in the Census Bureau’s
headquarters in Suitland, Maryland. For each record in sample, the “majority code,” in other words, the
industry or occupation code assigned most frequently among the multiple codes, was considered “correct”
for initial analysis purposes.
The Census 2000 coding staff at the NPC then re-coded each record in sample twice using the Census
2000 classifications. Lack of resources at the time prevented a third coding, which would have provided a
5 Note that in every census a code is assigned to every response, even if the respondent’s specified industry or occupation is not
listed in the index. Sometimes coding staff can derive a code from other information that the respondent provides, or simply
from an educated judgment. In census processing, this kind of coding-with-judgment is usually performed in a step called
“problem referral.”
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