Both income inequality in a state and the state’s primary care physician to population ratio are related to total mortality, infant mortality, and life expectancy at birth. Other analyses that also consider the effects of sociodemographic and socioeconomic characteristics on low birthweight show an effect of primary care on low birthweight as well. That is, greater primary care physician to population ratios are associated with lower death rates and better life expectancy.

Source: Shi L, Starfield B, Kennedy BP, Kawachi I. Income inequality, primary care, and health indicators. J Fam Pract 1999; 48(4):275-284.