Why has Argentina been unable to sustain a democracy? Why has establishing Iraq's been particularly dicey? According to the Harvard economist Edward Glaeser, it comes down to schools. If we want stable democracies, he writes, we need to invest in education. Being a numbers guy, though, he doesn't just argue the case philosophically. He's got data to back him up.What kind of data? The kind that shows that the more educated a country is, the more likely it is to have a strong democracy. You can read the entire report on international educations levels, and look at the data tables here.Maybe, then, if we start building schools in Afghanistan instead of sending troops, we can look forward to elections more successful than this last one.Map by Many Eyes