THE EFFECT OF UNDERCOUNT ON THE ACCURACY OF SMALL-AREA POPULATION ESTIMATES - IMPLICATIONS FOR THE USE OF ADMINISTRATIVE DATA FOR IMPROVINGPOPULATION ENUMERATION

The effects of underenumeration on the accuracy of alternative methods of population estimation have not been sufficiently analyzed. Althoug h the US Bureau of the Census has decided not to adjust either the cou nts or its estimates for underenumeration in 1990, the extent to which local population estimates may account for underenumeration is of imp ortance both for those who may wish to adjust existing estimates and i n anticipation of future census adjustments. This paper examines the a ccuracy of small-area population estimation methods with and without a djustment. Mean Percent Errors, Mean Absolute Percent Errors, and Mean Percent Absolute Differences between local estimates for 1990 and 199 0 adjusted and unadjusted census counts are computed. Population estim ates for 1990 made using housing unit, ratio correlation, and componen t methods are compared for 451 counties and 2,633 places in the states of California, Florida, Texas, and Wisconsin. An analysis of the data for counties shows little indication that local estimates more accura tely estimate the adjusted than the unadjusted population counts. The results for places show clear improvements in accuracy for places in F lorida and Texas. Implications of the findings for issues related to u ndercount adjustment and local population estimates are discussed.