The fed. gov¿t. has annually distributed over $300 billion in fed. assistance through grant programs using formulas driven in part by census population data. The U.S. Census Bureau puts forth tremendous effort to conduct an accurate count of the nation's population, yet some error in the form of persons missed or counted more than once is inevitable. Because many fed. grant programs rely to some degree on population measures, shifts in population, inaccuracies in census counts, and methodological problems with population estimates can all affect the allocation of funds. This testimony discusses: how census data are used in the allocation of fed. formula grant funds; and how the structure of the formulas and other factors can affect those allocations. Illus.