The equity-enhancing effect of primary care resources (primary care to population ratios) is shown in a study that examined postneonatal mortality rates in the 50 US states. Socially deprived states (those with high income inequality) had a 17% decrease (from average rates) if they were well endowed with primary care physicians, but a 7% increase in postneonatal mortality if they were relatively deprived of primary care physicians. States with relatively even distribution of income had a small positive effect of relatively high primary care physician to population ratio and a small negative effect (increased mortality) if primary care resources were relatively low.

Based on data in: Shi L, Starfield B. Primary care, income inequality, and self-rated health in the United States: a mixed-level analysis. Int J Health Serv 2000; 30(3):541-555.