Intertemporal Choice and Inequality

The permanent income hypothesis implies that, for any cohort of people, inequality in consumption and income should grow with age, a prediction that is here confirmed using data from eleven years of household survey data from the United States, twenty-two years from Great Britain, and fourteen years from Taiwan. In the permanent income hypothesis, the increase in inequality reflects the cumulative effect of luck on consumption. Other models of intertemporal choice--such as those with strong precautionary motives or liquidity constraints--can limit or even prevent the spread of inequality, as can insurance arrangements that share risk across individuals.