In the U.S., both taxes and old age Social Security benefits depend on one's marital status and tend to discourage the labor supply of the secondary earner. To what extent are these provisions holding back female labor supply? We estimate a rich life-cycle model of labor supply and savings for couples and singles using the Method of Simulated Moments (MSM) on the 1945 and 1955 birth-year cohorts and we use it to evaluate what would happen without these provisions.