Philip Howard explains:

The modern recipe for democratization includes several key ingredients. Wired civil society groups have proven particularly agile at sensitive moments for regimes, particularly during rigged elections. Only the regimes made wealthy through oil and natural gas reserves have had the resources to keep civil society actors at bay in these critical moments. Several significant political transitions over the last 15 years fit this recipe, as do recent cases of Egypt and Tunisia. Social scientists are loathe to predict, and rightly so. So instead of predicting political upheaval, it may be better to think about countries with the kinds of ingredients that go into the modern recipe for democratization.