There is a new paper out by them:
Thomas Piketty’s recent book, Capital in the Twenty First Century, follows in the tradition of the great classical economists, Malthus, Ricardo and Marx, in formulating “general” laws to diagnose and predict the dynamics of inequality. We argue that all of these general laws are unhelpful as a guide to understand the past or predict the future, because they ignore the central role of political and economic institutions in shaping the evolution of technology and the distribution of resources in a society. Using the economic and political histories of South Africa and Sweden, we illustrate not only that the focus on the share of top incomes gives a misleading characterization of the key determinants of societal inequality, but also that inequality dynamics are closely linked to institutional factors and their endogenous evolution, much more than the forces emphasized in Piketty’s book, such as the gap between the interest rate and the growth rate.
For the pointer I thank Nathaniel Bechhofer.