This paper exploits a major, unanticipated reform of the California teachers' pension to provide quasi-experimental evidence on the link between pension generosity and retirement timing. Using two large administrative datasets, the author conducts a reduced-form analysis of the pension reform and estimates a structural model of retirement timing. With both methods, the author finds that the rise in the price of retirement had a positive, but relatively small effect on the fraction of people retiring later. The implied estimates of the elasticity of retirement age with respect to the price of retirement are 0.02 in the medium-run and 0.10 in the long-run. With the baby boomers reaching retirement age, public officials and private pension managers are scrambling to design policy that will reduce the burden of pension obligations on younger workers and shareholders, while still fulfilling the promises made to those nearing retirement. The proposed reforms will inevitably alter key pension financial incentives faced by members, such as the reward for an additional year of work, making the degree to which these incentives affect retirement timing central to the policy debate. (Contains 8 figures, 3 tables, and 53 footnotes.)