About half of all attempted coups d'état fail

though coups against autocrats have sometimes led to democratization, more often they install a new set of autocratic elites and expose citizens to higher levels of repression.
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The data, again from Powell and Thyne (2011), show that about half of all attempted coups fail. The likelihood of failure varies with time period: 48% of attempted coups failed during the Cold War and 63% after it. In any case, regime change rarely follows failed coups: 6% of failed coups were followed by democratization and 3% by the establishment of a new dictatorship. In summary, coups fail frequently, and when they do, regime change rarely follows.
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From 1950 to 1989, 14% of successful coups against dictatorships led to democracy within two years, while 40% did so from 1990 to 2015.