The University of Chicago study also found African-Americans are less happy than whites and men are less happy than women.

Study author Yang Yang said the research relies on data gathered in the General Social Survey of the National Opinion Research Center.

Since 1972, the General Social Survey has asked a cross section of Americans the same question: "Taken all together, how would you say things are these days -- would you say that you are very happy, pretty happy, or not too happy?" The question was administered in face-to-face interviews.

The study, published in the American Sociological Review, found among 18-year-olds, white women are the happiest, with a 33 percent probability of being very happy, followed by 28 percent of white men, 18 percent of black women and 15 percent of black men.

However, black men and black women have just more than a 50 percent chance of being very happy by their late 80s, while white men and white women are close behind.

The baby boom generation was the least happy among those surveyed.