A positive theory of social security

In this paper I make two points. First, I argue that social security programs around the world link public pensions to retirement: people do not lose their pensions if they make a million dollars a year in the stock market, but they do confront marginal tax rates of up to 100 percent if they choose to work. Second, after arguing that most existing theories cannot explain this fact, I construct a positive theory that is consistent with it. The main idea is that pensions are a means to induce retirement—that is, to buy the elderly out of the labor force because aggregate output is higher if the elderly do not work. This is modeled through positive externalities in the average stock of human capital: because skills depreciate with age, the elderly have lower-than-average skill and, as a result, have a negative effect on the productivity of the young. When the difference between the skill level of the young and that of the old is large enough, aggregate output in an economy where the elderly do not work is higher. Retirement is desirable in this case, and social security transfers are the means by which such retirement is induced. The theory developed in this paper is also shown to be consistent with a number of other regularities documented in Section 1.