In developing a simulation model to estimate the cost of paid family and medical leave programs in a given state, we rely on data documenting known leave-taking behavior. Where this is not possible, we provide a set of reasonable assumptions about unknown aspects of behavior in the presence of a paid leave program. To obtain the estimates about known leave-taking behavior, we use the Department of Labor’s Family and Medical Leave 2000 Survey of Employees (hereinafter referred to as the DOL survey) to estimate behavioral models of leave-taking conditional on the demographic characteristics of individuals, combined with the Census Bureau’s March Annual Demographic sample of the Current Population Survey (hereinafter referred to as the CPS) to capture the demographic characteristics of individuals in individual states.