Whereas the vast majority of successful coups before 1990 installed their leaders durably in power, between 1991 and 2001 the picture reverses, with the majority of coups leading to competitive elections in 5 years or less.
We argue that with the end of the Cold War, outside pressure has produced a development we characterize as the “electoral norm” – a requirement that binds successful coup-entrepreneurs to hold reasonably prompt and competitive elections upon gaining power.
Consistent with our explanation, we find that post-Cold War those countries that are most dependent on Western aid have been the first to embrace competitive elections after the coup. Our theory is also able to account for the pronounced
decline in the non-constitutional seizure of executive power since the early 1990s. While the coup d’etat has been and still is the single most important factor leading to the downfall of democratic government, our findings indicate that the new generation of coups have been considerably less nefarious for democracy than their historical predecessors.
From a paper by Goemans and (my colleague) Marinov. There is a more recent version not yet online, but this older version should do.