What is the 1990 Undercount?
In a Census, some people are not counted. In
1990 we estimated the number of people not counted by conducting a
post-enumeration survey separately from the Census and comparing the
findings. The net undercount for 1990 is the difference between how many
people were actually counted in the 1990 census (the official count) and
the estimate of how many people lived in the United States at that time
(the adjusted count). The adjusted count is an estimate based on the
survey and the census enumeration itself. If the adjusted count is greater
than the official count, the difference is called an undercount. In a few
cases, the official count is greater than the adjusted count. When that
happens, we have an overcount, which we designate as a negative number.
The net undercount rate is the ratio of the net undercount to the adjusted
count; it is often expressed as a percent.
The data indicate that populations were
undercounted at different rates. In general, Blacks, American Indians and
Alaskan Natives, Asians and Pacific Islanders, and Hispanics were missed
at higher rates than Whites.
To cite an actual example, in the United
States overall, we estimate a net undercount of about 4.0 million people
in 1990, giving us an undercount rate of approximately 1.6%. The estimate
for Whites is about 1.8 million, for a rate of 0.9%. However, although
fewer Blacks (1.4 million) than Whites were missed, they were missed at a
higher rate, approximately 4.4%. Children were also disproportionately
missed in the last census. The net undercount for children - about 3.2% -
is twice the overall rate.
Using Undercounts and Undercount
When comparing the undercounts or undercount
rates for two geographic areas or demographic groups, one should be aware
that the numbers are measurements subject to sampling error.