Evaluating Public Programs with Close Substitutes: The Case of Head Start

This paper empirically evaluates the cost-effectiveness of Head Start, the largest early-childhood education program in the United States. Using data from the Head Start Impact Study (HSIS), we show that Head Start draws roughly a third of its participants from competing preschool programs, many of which receive public funds. Accounting for the public savings associated with reduced enrollment in other subsidized preschools substantially increases estimates of the program's rate of return. To parse Head Start's test score impacts relative to home care and competing preschools, we selection correct test scores in each care environment using excluded interactions between experimental offer status and household characteristics. We find that Head Start's effects are greater for children who would not otherwise attend preschool and for children that are less likely to participate in the program.