A growing number of Americans believe marriage is no longer necessary to start a family.

Nearly four in 10 - or 39 percent - of people polled say the institution is becoming obsolete, according to a new survey from the Pew Research Center conducted in coordination with Time Magazine.

"If four in 10 are saying it's becoming obsolete, they're registering an awareness of a very important social change," Pew researcher Paul Taylor told USA Today. "It doesn't necessarily mean marriage is about to disappear or has disappeared."

The report, which is supported by data from the U.S. Census Department, shows only 52 percent of adults 18 and over are married - an all-time low.

Four out of five of those surveyed say an unmarried couple with children or a single parent constitutes a family. And three out of five say a same-sex couple with children is a family.

The report is based on land-line and cell phone interviews conducted with 2,691 adults during the first three weeks of October. The survey had a margin of error of plus or minus 2.6 percentage points.