What has changed — and what seems to be the most likely explanation for the happiness trends — is that women now have a much longer to-do list than they once did (including helping their aging parents). They can’t possibly get it all done, and many end up feeling as if they are somehow falling short.

Mr. Krueger’s data, for instance, shows that the average time devoted to dusting has fallen significantly in recent decades. There haven’t been any dust-related technological breakthroughs, so houses are probably just dirtier than they used to be. I imagine that the new American dustiness affects women’s happiness more than men’s.

Ms. Stevenson was recently having drinks with a business school graduate who came up with a nice way of summarizing the problem. Her mother’s goals in life, the student said, were to have a beautiful garden, a well-kept house and well-adjusted children who did well in school. “I sort of want all those things, too,” the student said, as Ms. Stevenson recalled, “but I also want to have a great career and have an impact on the broader world.”

It’s telling that there is also a happiness gap between boys and girls in high school. As life has generally gotten better over the last generation — less crime, longer-living grandparents and much cooler gadgets — male high school seniors have gotten happier. About 25 percent say they are very satisfied with their lives, up from 16 percent in 1976. Roughly 22 percent of senior girls now give that answer, unchanged from the 1970s.

When Ms. Stevenson and I were talking last week about possible explanations, she mentioned her “hottie theory.” It’s based on an April article in this newspaper by Sara Rimer, about a group of incredibly impressive teenage girls in Newton, Mass. The girls were getting better grades than the boys, playing varsity sports, helping to run the student government and doing community service. Yet one girl who had gotten a perfect 2,400 on her college entrance exams noted that she and her friends still felt pressure to be “effortlessly hot.”

As Ms. Stevenson, who’s 36, said: “When I was in high school, it was clear being a hottie was the most important thing, and it’s not that it’s any less important today. It’s that other things have become more important. And, frankly, people spent a lot of time trying to be a hottie when I was in high school. So I don’t know where they find the time today.”

The two new papers — Mr. Krueger’s will be published in the Brookings Papers on Economic Activity and the Stevenson-Wolfers one is still in draft form — are part of a burst of happiness research in recent years. There is no question that the research has its limitations. Happiness, of course, is highly subjective.