We investigate how the shift in private pension coverage from defined benefit (DB) to defined contribution (DC) retirement plans since the 1980s has contributed to the substantial rise in labor force participation of older Americans. We develop a life cycle model of retirement that captures important aspects of private (DB and DC) and public (Social Security Old-Age) pensions. We demonstrate how this novel framework can assist policy makers and researchers in analyzing the complex interrelations of labor supply decisions, retirement behavior, and wealth accumulation.