When the mean impact of an assigned social program cannot be estimated due to non-feasibility of a pre-intervention baseline survey, it is possible to track the ex-participants instead. By developing a triple-difference estimation model, measured outcome changes are compared between present participants and ex-participants. With sufficient follow up observations one can test the joint conditions required for correctly identifying the gains to the present participants. The same method, when applied to a program in Argentina, reveals significant impacts on participants' incomes.