What's behind the decline in female happiness?

It's enough to give even the most unflappable wife, mother and career woman a bad case of the blues: Last fall, University of Pennsylvania researchers Betsey Stevenson and Justin Wolfers caused a stir when they published a paper in the American Economic Journal bearing the ominous title "The Paradox of Declining Female Happiness."

The pair, both faculty members at the Wharton School of business, found that women in the United States are less satisfied with their lives than they were 30 years ago, while men report feeling more contented - findings that were consistent across racial, economic and age groups.

In 1972, Stevenson says, the women who ranked at the 50th percentile for happiness were as happy as men who ranked at the 53rd percentile for their gender. But by 2006, women at the midrange were only as happy as men who placed in the 48th percentile for their gender.

The change "might not seem like a lot, but it's huge," she says.

"That's a similar decline in happiness to what you'd expect to see if unemployment rose from 4 percent to 12 percent."

And that's puzzling, she says, because, by almost any measure, women's lives have improved in the past three decades: Women are better educated and have made inroads into professions that previously were all-male. The wage gap has decreased and women live longer.

"There are a lot of potential explanations for the decline in female happiness," Stevenson says. "One is that our expectations have risen, and society hasn't been able to fully deliver. Women also are trying to succeed in more domains than we once did . . . having a good marriage, happy kids and a well-kept home. . . . If she falls short in any one area, it will affect how happy she considers herself to be."