New data gathered by the Census, larger computers, and significant advances in the statistical and mathematical treatment of demographic variables make it possible to conceive of a system of National Interregional Demographic Accounts. Such a system of accounts would subdivide the nation into a number of areas, possibly as fine as counties, and provide a complete picture of their population changes through births, deaths, migratory flows from all other localities and from abroad. It would be superior to the individual analyses and projections of particular localities by recognizing the interdependence of all localities, linking intimately the past and future history of each with those of the rest of the system. This system of accounts could be used to make projections of the national distribution of population under alternative birth rates, and it would serve to test the direct and indirect consequences of a variety of alternative national growth policies.