American women are wealthier, healthier and better educated than they were 30 years ago. They’re more likely to work outside the home, and more likely to earn salaries comparable to men’s when they do. They can leave abusive marriages and sue sexist employers. They enjoy unprecedented control over their own fertility. On some fronts  graduation rates, life expectancy and even job security  men look increasingly like the second sex.

But all the achievements of the feminist era may have delivered women to greater unhappiness. In the 1960s, when Betty Friedan diagnosed her fellow wives and daughters as the victims of “the problem with no name,” American women reported themselves happier, on average, than did men. Today, that gender gap has reversed. Male happiness has inched up, and female happiness has dropped. In postfeminist America, men are happier than women.

This is “The Paradox of Declining Female Happiness,” the subject of a provocative paper from the economists Betsey Stevenson and Justin Wolfers. The paper is fascinating not only because of what it shows, but because the authors deliberately avoid floating an easy explanation for their data.

The decline of the two-parent family, for instance, is almost certainly depressing life satisfaction for the women stuck raising kids alone. But this can’t be the only explanation, since the trend toward greater female discontent cuts across lines of class and race. A working-class Hispanic woman is far more likely to be a single mother than her white and wealthy counterpart, yet the male-female happiness gap holds in East Hampton and East L.A. alike.