The bottom line of my joint review of The Hunger Games and Why Nations Fail is that political change is hard. Countries with dysfunctional political structures fare poorly and produce discontent and injustice, but oftentimes the new leadership simply takes control of the old bad institutions. Eric Chaney's new paper (PDF) on the Arab Spring applies a similar analysis to the "democratic deficit" in the Arab world. He shows that "the percent of a country’s landmass that was conquered by Arab armies following the death of the prophet Muhammad statistically accounts for this deficit." In particular, he argues that you can't say that specific elements of "Arab culture" account for the deficit because it's present in non-Arab countries as well. But you also can't say that specific elements of "Muslim culture" account for the deficit because it's not present in Muslim-majority countries that weren't part of the original Arab conquest:
Once one accounts for the 28 countries conquered by Arab armies, the evolution of democracy in the remaining 15 Muslim-majority countries since 1960 largely mirrors that of the rest of the developing world.
He then spins out a story about the institutional legacy of the Arab conquest and its long-term impacts. I'm sure historians and regional specialists will find plenty not to like in his rather breezy treatment of the details (and of course social scientists everywhere have grievances about economists' imperialistic ambition to conquer all other fields), but the basic statistical point is striking.