What determines successful reform in developing countries?

Daron Acemoglu, Simon Johnson, Pablo Querubín and James A Robinson nail it:

One can find instances where the root of these distortionary policies is in mistaken economic theories. But this is the exception rather than the rule. Few policymakers create insurmountable entry barriers, hyperinflations or large budget deficits because they think this is good for the economy. Instead, the root of distortions lies in political economy. In most instances, bad policies are adopted because of political economy constraints and distorted incentives facing politicians in many societies with poor general institutions, such as weak checks and balances and lack of political accountability.

This seems to me exactly right; and it is something that not everybody understands.