William Easterly relies on his own research as support for parts of chapter 13 from "The Elusive Quest for Growth", although it isn't only income inequality that hinders economic growth. Rather it is mixed in with other elements that tend to divide societies. In his paper "The Middle Class Consensus and Economic Development", he finds greater homogeneity of the population and a greater share of income going to the middle class is associated with higher incomes and higher economic growth. Here is the abstract for the paper: "Modern political economy stresses "society's polarization" as a determinant of development outcomes. Among the most common sources of social polarization are class divisions and ethnic divisions. A middle class consensus is defined as a high share of income for the middle class and a low degree of ethnic divisons. A middle class consensus distinguishes development successes from failures. The paper links the existence of a middle class consensus to exogenous country characteristics like resource endowments, along the lines of the provocative thesis of Engerman and Sokoloff 1997 that tropical commodity exporters are more unequal than other societies. This hypothesis is confirmed with cross-country data. This paper exploits this association using resource endowments as instruments for inequality. A higher share of income for the middle class and lower ethnic divisions are empirically associated with higher income and higher growth. These associations are robust to a number of alternative controls. A middle class consensus is also associated with more education, better health, better infrastructure, better economic policies, less political instability, less civil war and ethnic minorities at risk, more social 'modernization' and more democracy." He refined this thesis in a later paper titled "Social Cohesion, Institutions and Growth", which will be published next month. Now he argues that social cohesion, as measured by income inequality and ethnic fractionalization, endogenously determine institutional quality, which in turn determines growth. The papers are available on the research page of his website: http://www.nyu.edu/fas/institute/dri/Easterly/Research.html Brad Andrew