The Population Estimates Program in the U.S. Census Bureau Population Division develops and disseminates the official estimates of the population of the United States. As part of this program, it produces annual estimates of the population of counties by age, sex, race, and Hispanic origin. These estimates are used to develop the population controls to the American Community Survey (ACS).

The Census Bureau employs population controls in its survey process both to reduce the variance and to reduce the bias caused by the differential coverage of population groups in the survey. Recently, members of the Census Advisory Committee of Professional Associations (CACPA) have questioned the use of these population controls in the ACS. More specifically, the members have asked about the accuracy of these population estimates by demographic characteristics at the county level. The accuracy of a set of population estimates is traditionally measured by comparing a set of population estimates prepared prior to a decennial census to the decennial census results. However, limitations such as differential coverage in censuses and changes in race categories need to be considered when evaluating the results of such comparisons.

To provide information about the accuracy of the population estimates by age, sex, race, and Hispanic origin, we compared a set of 1990-based population estimates by demographic characteristics to Census 2000 results. This paper presents the results of these comparisons for the population estimates for the nation, states, and weighting areas used in the Census 2000 Supplementary Survey (C2SS). The paper includes a discussion of the limitations of such an evaluation and outlines the issues that must be considered when using these results as a measure of the accuracy of the population estimates developed for the post-2000 decade.