Married Batters Paid More than Equally Good Bachelor Batters
(p. C4) Many studies have found that married men earn more than their single peers, but whether they're actually more productive is harder to answer. To settle the question, researchers looked to baseball.
They took a random sample of nearly 3,500 pro hitters, from 1871 through 2007, comparing their batting averages and other statistics with their salaries (as revealed in MLB archives and other sources). Until 1975, when the market for players became freer, there was no link between marriage, productivity and earnings. After 1975, there was some evidence that hitters who begin their careers in the bottom third of the ability spectrum gained a handful of points in batting average when they married, and a bit of salary, but the evidence was statistically weak.
For the full summary, see:
The paper summarized is: