It's been a tough month for dictators. Yesterday, Sudan's longtime leader Omar Bashir was toppled in a military coup after prolonged unrest across the country. That came just a week after Algeria's ailing autocrat Abdelaziz Bouteflika resigned after popular protests prompted his own generals to turn on him. So, should the world's tyrants be quaking in their boots? Maybe not just yet. Coup attempts are far less common today than in the past – and they are also less successful. Here's a look at the historical record.