Blogger "Those Who Can See" offers a global introduction to differing rates of corruption.
Audacious Epigone calculates a moderate 0.44 correlation coefficient between perceived levels of corruption by country and cousin marriage rates.
U. of Chicago economist Luigi Zingales has a new book coming out, A Capitalism for the People, about growth of Italian-style corruption in America and what a pro-market populism can do about it. He even points out that economists may not be immune to the workings of self-interest!
An important point is that the dominant Who? Whom? media reflexes get in the way of noticing corruption. Simple concepts such as "conflict of interest" are much less often applied to those claiming to represent favored groups, such as self-appointed Hispanic activists threatening electoral ruin for any statesman unenthusiastic about more immigration.
For example, we have a persistent problem of gay corruption in some of our institutions, where homosexual harassers of boys and young men are shielded by other homosexuals in power. But the concept of "gay corruption" has largely been purged from 21st Century consciousness. Gays are Good, homophobes are Bad, that is all you need to know. So it's very hard for people to notice patterns. And pattern recognition is bad, too.