Does more wealth mean less political corruption?

When it comes to the international pattern of corruption, the beginning of wisdom is to know how little we know. I have been studying the topic for almost 20 years, and progress has involved many steps back as well as forward. Despite tens of thousands of papers written by scholars during that period, virtually the only thing one can say with confidence today is that richer countries, such as the United States, tend to have cleaner government than poorer ones.