Most workers contribute to Social Security throughout their working lives and receive benefits after they retire. The balance between lifetime contributions and benefits determines the program’s sustainability and progressivity. This brief uses DYNASIM, the Urban Institute’s dynamic microsimulation model, to project lifetime benefits and taxes for people born between 1940 and 1999. The results show that most nondisabled beneficiaries who survive to age 65 are scheduled to receive more in benefits than they contribute in taxes. The benefit-to-tax ratio is higher for those with lower lifetime incomes and is projected to remain stable over time for each quintile of lifetime income.