According to a recent article  in Harvard International Review, because of differences in fertility, the population growth rate in dictatorships is higher than that in democracies at every income level. It says "an average woman has one-half of a child more under dictatorship than under democracy." As a result of this faster population growth, dictatorships have greater GDP growth even though they have lower per capita GDP growth compared to democracies.
This information leads me to ask a couple of questions: 1. Why is fertility higher in dictatorships? Do dictators like bigger populations, and democrats like smaller populations? Does population growth influence choice of government? Or is there a third factor that affects both fertility and form of government? 2. Should economists try to maximize GDP, or per capita GDP? If the former should they be supporting dictatorships? Another interesting piece of information in this article is that democratic regimes are more frequent in more developed countries, but it's not because those countries are more likely to become democracies. Rather it's because they are less likely to revert back to dictatorships. Among democracies that have collapsed, the one with the highest per capita income is Argentina in 1975 -- US$6055.  A Flawed Blueprint. By: Przeworksi, Adam. Harvard International Review, Spring2003, Vol. 25 Issue 1, p42.