Everyone agrees about Southern Europe
What's interesting here is that there actually doesn't seem to be much disagreement about Southern Europe. Sumner references explanations "tied to cultural differences" as the main ones he's heard -- in other words, it's nothing to do with welfare state design. But he dismisses that as an inadequate response for progressives to offer because those are "conservative explanations." But Robert "Making Democracy Work: Civic Traditions in Modern Italy" Putnam isn't a conservative. When I asked Cowen how he explains Southern Europe he pointed to Edward Banfield's "Moral Basis of a Backward Society". Francis Fukuyama has also treated the subject well in his recent books "The Origins of Political Order" and "Political Order and Political Decay".