In a path analysis taking income inequality into account, the supply of primary care physicians in the 50 US states is significantly associated with less infant mortality, lower total mortality, and higher life expectancy.

(In contrast to international comparisons, there is no relationship with low birth weight, probably because of the many sociodemographic influences and poor maternal health care in vulnerable populations in the US. )

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