12  The literature on the reasons for the rise in inequality is extensive, but one recent work that tries to address the issue is David H. Autor, David Dorn, and Gordon H. Hanson (2013), “Untangling Trade and Technology: Evidence from Local Labor Markets,” NBER Working Paper Series 18938 (Cambridge, Mass. : National Bureau of Economic Research, April).
13  For a discussion of mobility in income distribution, see Raj Chetty, Nathaniel Hendren, Patrick Kline, Emmanuel Saez, and Nicholas Turner (2014), “Is the United States Still a Land of Opportunity? Recent Trends in Intergenerational Mobility,” NBER Working Paper Series 19844 (Cambridge, Mass. : National Bureau of Economic Research, January).