[Excerpt] Budgetary pressures on the Social Security system have increased in recent years, prompting a variety of proposals to restructure the U.S. retirement income program. Most of these proposals ignore the possibility that the retirement patterns of older workers are likely to respond to changes in the incentives to retire. This chapter presents two important pieces of information for policymakers. First, we provide previously unavailable evidence on how changes in the structure of Social Security benefits would alter the economic incentives to retire at different ages. Second, we compute how retirement patterns would change in response to altered incentives to work at later ages.