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

“majority” choice in most cases when coders assigned different codes to the same records. So the first of
the two codes assigned was used for initial analysis purposes.
The selected 1990 and 2000 codes were then cross-tabulated against each other, creating a matrix of
1990-by-2000-code combinations similar in concept to the cross-tabulation of codes assigned to the index
lines described in the section above. The distributions of responses to these 1990-by-2000 combinations
were then compared to their 1990-by-2000 counterparts created from the 2000 classified index.
These comparisons exposed the fact that coding errors can contaminate the analysis of changes in the
labor force from the 1990 classifications to the 2000 systems. Remember that the index crosswalks
provided a set of expected changes from 1990 to 2000. The distributions of actual responses, however,
often did not match the expected distributions as measured by the index. Many combinations of 1990 and
2000 codes appearing in the 1990 Census Sample did not appear at all in the index crosswalk, and made
no logical sense together.
Census Bureau staff identified and examined many of the worst discrepancies between the two sets of
distributions. Once again, this examination revealed errors in the index that caused coding errors, but were
not caught in the original review of the index described above. Fortunately, this first review of the Census
Sample occurred before the Census 2000 processing, so the indexes could be repaired in time for the
actual census. At the same time, these coding errors plus others that were not caused by the index were
corrected in the 1990 Census Sample.
After the census was completed, staff revisited the 1990 Census Sample and once again compared its
1990-2000 distributions (after the revisions resulting from the first review) to those found in the index
crosswalks. This comparison instigated a second review of the sample, particularly for those 1990 codes
that showed the largest discrepancies between the sample and the index. Over 18,000 of the 146,000+
records in sample were reviewed. This examination led to the correction of more coding errors, and to the
deletion of records containing responses that were judged to be too vague to code accurately. Most of
these deletions had no clear “majority” among the multiple codes assigned over the years since 1990.
Altogether, over 5300 records were corrected or deleted.
Calculation of the Conversion Factors
Because the index crosswalk represented the expected distribution of the 1990 categories into the 2000
classifications, this source became the starting point for determining which 1990 to 2000 code
combinations were “legitimate.” In other words, the starting assumption was that the combination of
1990-2000 codes among the index titles ideally should drive the assignment of those codes to actual
census responses.
This assumption, therefore, initially eliminated records in the 1990 Census Sample that contained 1990-
2000 code combinations that did not appear in the index crosswalk. In other words, the corollary to this
assumption was that any records in the 1990 Census Sample that did not contain a “legitimate” 1990-2000
code combination must contain coding errors that make the records ineligible for inclusion in the
computation of conversion factors. The factors used to adjust or redistribute the 1990 tabulated data into
the 2000 classifications should not make non-logical conversions based on errors in the sample that
created those factors.
12