Subcounty Population Forecast Accuracy: An Analysis beyond Size and Growth

Stefan Rayer, University of Florida
Stanley K. Smith, University of Florida

Population forecasts for subcounty areas are used for a wide variety of planning and budgeting purposes. Given the importance of many of these uses, it is essential to investigate which techniques and procedures produce the most accurate forecasts. In this paper, we describe several trend extrapolation techniques as well as averages and composite methods based on those techniques. Using data from 1970–2005 for subcounty areas in Florida, we evaluate the precision and bias of forecasts derived from these techniques. We also assess the effects of differences in population size, growth rate, and length of forecast horizon on forecast errors, and investigate the impact of adjusting forecasts to account for the effects of annexations and changes in special populations. We believe the findings presented in this paper will help practitioners make informed decisions when they construct and analyze population forecasts for subcounty areas.