An Evaluation of Texas Population Estimates and Projections Program’s Population Estimates and Projections for 2000

Nazrul Hoque, University of Texas at San Antonio

Population estimates and projections are difficult to complete with accuracy for small areas (Murdock et al., 1991; National Academy of Science, 1980; Ascher, 1978). As a result, it is essential that any ongoing program of population estimation and projection periodically evaluate the results of past estimation and projection efforts against actual counts of the population (Murdock and Ellis, 1991). Only by assessing the accuracy of past efforts it is possible to know the nature of errors made and to take steps to improve future estimates and projections. In this paper, we evaluate the accuracy of the Texas Population Estimates and Projections Program’s population estimates and projections for 2000 compared to the 2000 Census Counts for counties and places in Texas. For estimates, we evaluated Component Method II, the Ratio-correlation Method, and the Housing Unit Method. Three error measures are used to asses the accuracy of estimates and projections. They include the Mean Percent Error (MPE), the Mean Absolute Percent Error (MAPE), and the Mean Percent Absolute Difference (MPAD). This later measure is also referred to as the weighted mean absolute percent error. The evaluation of the Texas Population Estimates and Projections Program’s population estimates presented here suggests that the estimates are generally adequate and show levels of error that, when compared to the 2000 Census Counts, are within generally accepted ranges. They also show the expected patterns by population size and population change. Of the several methods tested, no single one produced more accurate estimates than the average of two or three methods. The assessment of the accuracy of the place-level estimates showed substantially higher levels of errors than those found for counties, and provided the basis for the revision of our estimates procedures for the 2000s.