# Key Takeaways 1. [[relationship between income inequality and population health]]| As Preston surmised, there is indeed a relationship between income and mortality within rich countries, even those on the flat part of the international curve. # Notes [[Preston Curve]] If these curves come from a causal link between income and health, income redistribution will improve population health. It is often useful to think of the redistributive story, not in terms of inequality, but in terms of poverty. If a country with a high average income has a great deal of income inequality, then there is a relatively large number of people with low income whose [[health is]] poor. And if a rich country has a lot of poor people, it will have low average health relative to its per capita income. It should be noted, however, that recent increases in income inequality, though large enough by postwar standards, are probably not large relative to earlier compressions, particularly those associated with the world wars (see Peter Lindert 2000, and Claudia Goldin and Lawrence Katz 2001). ==They are also characterized more by increases in the incomes of the rich than by decreases in the incomes of the poor.== ## 2.1.2 Does Income Cause Health? The nonlinearity argument for income redistribution, in common with almost all of the literature in epidemiology and public health, takes it for granted that increases in income cause improvements in health and reductions in mortality. Yet ==Preston’s original paper emphasized that income is only part of the story, and he shows that the curves have shifted upward over time, a movement that he attributes to improved public health measures, particularly in middle-income countries==. And the 2000 Preston curve in figure 1 has developed a non-monotonicity around $5,000, driven by the collapse of life expectancy in Russia, and by AIDS in Africa, particularly in South Africa; neither of these developments is income driven. ## 2.1.4 Relative Income, Absolute Income, and Inequality That health depends on income relative to average incomes of one or more reference groups is what we might call a relative income hypothesis. One case is where relative income determines access to material goods, for example when the people who live in a town are the market for local land for housing, with the richest getting the hilltop plots with fine views, and the poorest getting the plots downwind of the smokestacks. ## 2.3 Income Inequality as a Consequence of Ill Health Most of this section has started from the position that income causes health, developing the consequences for the relationship between income inequality and health. But health also causes income, and policies that directly affect health are likely to have effects on income inequality. When interactions between income and health are important, the distribution of income will depend on the level and distribution of health. Any measure that reduces the spread of health conditions across the population, or improves the health environment, will narrow the distribution of income. Health shocks are important determinants of earnings and consumption in developing countries;