The Social Security debate is focused on mundane financial issues: transition costs, benefit adequacy, the value of the Social Security Trust Fund, and so on. The program’s long-term impact on individual economic choices is much more important but generally neglected. Completely unheard in the debate, however, is the program’s potential to affect fundamental choices about family formation. A new study by Michele Boldrin and colleagues examines the link between government-provided old-age pensions and the continual dramatic reduction in fertility throughout the developed world during the twentieth century. Its compelling evidence suggests an issue that deserves serious attention as policymakers consider the future of Social Security.