Why are political systems more democratic in certain countries at certain times and less so in other countries at other times? We may think of this very big question as containing a group of somewhat smaller, though still substantial, questions: Why do movements for democracy arise at certain times and places? Why do regimes sometimes claim to be making “democratic” changes? Why do some of these democratic regimes endure for relatively long periods while other experiences of democracy prove to be fleeting? And why do multicontinental waves of democratization (and waves of antidemocracy) arise? When we look at the pattern of democracy in the world, the timing of democratic waves, and the durability of the democratic transformations in different places, we will find that many social processes play a role.