The Right People, the Right Rates: Making Population Estimates and Forecasts with an Interregional Cohort-Component Model

Innocent looking technical choices can cause large differences in population projections. This article offers suggestions for making those choices and creating a more thoughtful population forecasting process. Emphasis is on an interregional cohort-component approach made possible by newly available inmigration and out-migration data for all counties. The interregional approach avoids conceptual problems and biases of conventional net migration approaches and can be used to make county population estimates, projections, and forecasts. Sample spreadsheets with formulas demonstrate the procedures for calculating rates and making projections. Population projections for fifty-five counties illustrate the effects of several methodological choices.