Estimates are made, from time series data on real gross domestic products, of the standard deviations of returns in markets for perpetual claims on countries' incomes. The results indicate that the variability of returns is of a magnitude comparable to that of returns in stock markets. Evidence...

Social security system old age insurance systems are devices for the sharing of income risks of elderly people with others. Risks can be shared intergenerationally (with the young of the same country), intragenerationally (with other elderly of the same country), or internationally (with...