It is widely observed that married men earn more than single men. But does marriage cause a man to earn more, or it's just because more productive men are more likely to get married?
Kate Antonovics and Robert Town's research suggests that marriages likely cause men to earn more. According to the research, which is based on monozygotic twins (i.e. brothers with the same genetic code and raised in the same family) with the same education, married men earn an average of 27% more than his unmarried brother.
The full text of the 9-page paper, cleverly named "Are All the Good Men Married? Uncovering the Soures of the Marital Wage Premium", is available in PDF format.
I read the paper and it is pretty convincing. If you don't especially feel for reading academic papers, here are some news coverage for the study.
New York Times: Analyzing the Marriage Gap
Kiplinger's Personal Finance: Marriage Prospects: Richer, not Poorer
Lexington Herald-Leader: Men, It pays to be married