The Pew Research Center just published a piece reviewing their finding that people who are married report significantly greater levels of happiness than those who are unmarried. I always enjoy this result, particularly because of contemporary Western culture’s uneasy relationship with the institution of marriage.

What I would really like to see, though, is a graph that plots the relative difference in happiness between people who are married and unmarried as a function of the number of years of marriage. I’m entirely willing to concede that the difference is always positive, but I have the suspicion that it’s also decreasing on at least some intervals. It would be fascinating if the opposite were the case — assuming, of course, that one had controlled for the obvious selection effect that the couples who will stay married longer are almost by definition the couples that are happier, so that it’s a foregone conclusion that the level of happiness will increase with the length of the marriage.