The group, now aged 18 to 33, are also the most racially diverse generation in U.S. history, the Pew Research Center reported. About 43 percent are non-white, many of them the children of Asians who immigrated to the United States in the last half of the 20th century.
While half of millennials say they are political independents, they are more likely to have views that would be described as liberal. That includes support for same-sex marriage and for a larger role for government.
They also tend to vote Democratic.
Almost one-third, 29 percent, of respondents said they are not affiliated with a religious group.
The survey found millennials were less likely to be married than their elders were at the same age. Only 26 percent had tied the knot, compared to 36 percent of Generation Xers, 48 percent of Baby Boomers and 65 percent of the Silent Generation.
Childbirth without marriage was more common, with 47 percent of millennials' children born outside wedlock.
Pew interviewed 1,821 adults across the country between Feb. 14 and Feb. 23, including 617 millennials. The margin of error is 2.6 percentage points.