New polling data indicates more Americans want to cohabitate before marriage and more than half of all Americans think marijuana should be legalized. NBC's Brian Williams reports.

A majority of Americans are in favor of legalizing the use of marijuana, a national survey finds, a shift in attitude after more than four decades of polling on the issue.

Fifty-two percent of Americans say the use of marijuana should be made legal, while 45 percent say it should not, according to a Pew Research Center survey conducted in March among 1,501 adults. People aged 18 to 32 are the most supportive group, but half of baby boomers now favor legalizing marijuana, too.

The survey shows the acceptance rate has risen 11 points since 2010. The shift is even more dramatic when taking into account a 1969 Gallup survey showing that only 12 percent of Americans favored legalization.

The survey finds that almost half of Americans -- 48 percent -- say they have tried marijuana, up from 38 percent a decade ago. About 12 percent say they have used marijuana in the past year.

Fewer Americans now perceive marijuana as a gateway drug, and fewer say that smoking marijuana is morally wrong. The survey also shows about 72 percent believe government efforts to enforce marijuana laws cost more than they are worth. In November, Colorado and Washington state voted to approve the recreational use of small amounts of marijuana.

But while more and more Americans are in favor of legalization and fewer perceive marijuana as a dangerous drug, the survey shows about half say they would still feel uncomfortable if people around them were using marijuana.