Industry mix, wages, and the divergence of county income in Pennsylvania

Per capita incomes have diverged across Pennsylvania counties. County incomes may differ because of differences in industrial structures and because of differences in earnings within industries; a county may have a below-average income because its industry mix is comprised of low paying jobs or because county jobs pay low wages compared to the same jobs in other counties. A procedure developed by Hanna (1951) is utilized to separate income differences into these two components by constructing two counterfactual incomes for each county. The handful of high-income counties in Pennsylvania have favorable wages while the counties with incomes below the state average, although with employment mixes comparable to the overall state mix, tend to have workers who receive low wages relative to the state industry average. Wages are low in the relatively poor counties due to less investment in physical and human capital.