This great chart from The Economist sums it up - in the '60s through '80s there were an average of 12 military coups or attempted coups a year. 1963 alone saw 25! That's what happens when large swaths of the world (namely Africa and Latin America) tumultously decolonize and don't yet have the capability for stable democracy - they become susceptible to violent military takeovers. But that's been declining, and around 1992, it really started improving fast - especially without the United States and Russia bankrolling distant rebellions against each other. In 2007 there was only one effort. Looks like governments and their peoples have grown less willing to recognize those who shoot their way into office, preferring to use the ballot box instead.