Physical impairment and the diminishing effect of income

The effect of income on physical impairment steepens at lower levels of income. Why? Two national surveys show the following. Basic needs: the level of impairment and its rate of increase rise sharply as household income drops below the 20th percentile; above that level greater income has little effect; economic hardship explains much of the pattern. Resource substitution: education reduces the association between impairment and low income, but low education often coincides with low income. Compounding problems: impairment suppresses the rise of income, concentrating economic and health problems over time. Status lifestyle: Exercise increases with income but explains little of the association with impairment. Social background: stable traits that affect both income and impairment account for about half of their association, with education the largest factor.