Wilkinson and Pickett are quite helpful in laying out certain income inequality dataas well as data on a wide and impressive array of correlated social problems and issues. They rely on comparisons within two samples: the twentythree richest countries and the fifty states in America. They discuss some of the relevant theories and at least some of the relevant literature. Then, they combine the data, theory, and literature review with some just-so stories that result in inferences somewhere between solid ground and an awkward narrative that fits various aspects of their worldview. At the end of the day, their data do not imply much about how to achieve their ends.
D. Eric Schansberg, "Review Essay: Not Quite on the Level," Journal of Markets & Morality 18, no. 1 (Spring 2015): 199-206