In the United States and other developed countries, women have a lot to be happy about. More than ever before, they can enjoy the same educational and career opportunities as men. Even at home, domestic dynamics have become more of a shared burden rather than women's work. Somehow, amid the progress, a 2008 analysis from economists at the University of Pennsylvania found that American women today aren't as happy as they were 30 years ago. The authors of the paper explain the decline in happiness in terms of skyrocketing unemployment rates -- from 4 percent to 12.5 percent [source: Wilson Quarterly].
Princeton economists have also come to the same conclusion about women's sagging happiness. By exploring how much women enjoy common activities, such as gardening or watching television, it seemed that they spend more time on less gratifying undertakings. In any given week, women spend an average of 90 more minutes than men performing "unpleasant" tasks [source: Leonhardt]. This trend likely relates back to women's achievements in recent decades. With more prospects outside of the home, many women are experiencing difficulty balancing a career and a family, which saps happiness.
Age has also emerged as a determining factor for whether men or women are the happier sex in the United States. A study in the Journal of Happiness Studies established 48 as the benchmark age when men's happiness overtakes women's. As younger adults, women find more joy in building families and lasting relationships, while men are struggling to climb the job ladder. By middle age, the tables supposedly turn as women face the disappointment of not realizing life goals and men reach theirs. Then, at 64, men begin to appreciate their families even more than women [source: Byner]. But that age-happiness correlation may be tied to geography. Across the pond, a 2008 University College London survey found that women 50 years old and older are more optimistic than their male counterparts [source: Alleyne].
So who wins the happiness battle of the sexes? At the end of the day, both males and females can look forward to sunnier old age. No matter the number of X chromosomes, adults show a consistent spike in reported happiness once mid-life crises subside.