With fixed costs of participating in the stock market, consumers with high income will participate in the stock market, but consumers with lower income will not participate. If a fully-funded defined-contribution social security system tries to exploit the equity premium by selling a dollar of...

In the presence of uncertain lifetimes, social security has the characteristics of an annuity: a consumer pays a tax when young in exchange for receiving a social security benefit if he survives to be old. If consumers have identical ex ante mortality probabilities, then a fully funded social...