This article evaluates the effects of maternal vs. alternative care providers' time inputs on children's cognitive development using the sample of single mothers in the National Longitudinal Survey of Youth. To deal with the selection problem created by unobserved heterogeneiTY of mothers and children, we develop a model of mother's employment and childcare decisions. We then obtain approximate decision rules for employment and childcare use, and estimate these jointly with the child's cognitive abiliTY production function. To help identify our selection model, we take advantage of the plausibly exogenous variation in employment and childcare choices of single mothers generated by the variation in welfare rules across states and over time created by the 1996 welfare reform legislation and earlier State waivers.
