Tools for Integrating Cohort-Component Projections

Peter Johnson, U.S. Census Bureau

The U.S. Census Bureau’s Subnational Projections Toolkit supports two types of cohort-component subnational projection approaches, referred to as “bottom-up” and “top-down.” The bottom-up approach can be used if the quality of data for subnational areas is considered good. In this approach, national-level estimates and projections are calculated as the sum of subnational estimates and projections. These projections can be performed using the Rural-Urban Projection (RUP) and RUPAGG programs. The top-down approach, conversely, assumes that national-level figures are more reliable than those at the subnational level and that, therefore, the subnational estimates and projections should be adjusted to be consistent with the independent national figures. The RupSubAdj workbook takes preliminary RUP projections for the subareas and a final RUP projection for the national population and adjusts the subnational projections to agree with the national projection populations, deaths, migrants, and births by single years of age for each year of the projection.