Are rich people more likely to be jerks, or are jerks more likely to get rich?

A new study came out saying that rich people are more likely to take candy from children, break the law while driving, lie in negotiation, cheat to increase their odds of winning a prize and endorse unethical behavior at work.

Which then leaves the causation/correlation question: Are rich people more likely to be jerks, or are jerks more likely to get rich?