WASHINGTON -- A new public opinion survey is the latest to confirm a major social trend that shows no sign of ebbing: rising acceptance of same-sex marriage and homosexuality in America. Fully one in seven adults (14%) say they've changed their mind about gay rights, often because they have a friend or family member who is gay, according to the new national poll by the independent Pew Research Center. Recently, another national poll, by the Washington Post and ABC News, found that support for gay marriage is now at an all-time high, as the Supreme Court prepares to take up the issue, including a test of California's Proposition 8, which banned same-sex marriages. The Pew poll shows less lopsided support for gay marriage than the Post/ABC poll, but both surveys reflect similar shifts in favor of same-sex unions. The Pew poll also traces the causes of the wider social shift, one of the biggest on any issue question over the past decade. These roots are worth examining, even if some may not seem overly surprising - like the fact that the emergence of a younger, more tolerant generation has a lot to do with the overall change in public attitudes. In the 18-32 age bracket, support for same-sex marriage is at 70%. Ten years ago, among members of the same generation, it was 51%. But support for same-sex marriage has also increased among those born between 1928 and 1945; in 2003, just 17% were in favor, and today that figure is 31%. Among those who've changed their minds about gay marriage, one in four (25%) say it's just because they've grown older. One in five (20%) say today's world is different and this change is inevitable. Nearly as many (18%) say they think that government should no longer intrude in people's lives in this way and that individuals should be free to do what makes them happy. Almost one in three (32%) say it's because they know someone who is gay. And 13% credit a belief in individual rights or various moral or religious teachings for their change of heart. The shifting attitudes toward same-sex marriage closely track changing opinions about homosexuality. Today, a slight majority of Americans (51%) says that same-sex marriage isn't a threat to traditional families. A decade ago, when Massachusetts became the first state to permit same-sex marriage, most people (56%) said the practice would undermine the traditional family and only 39% said it wasn't a threat. Evolving opinions toward gay and lesbian rights closely resemble other social and political divides, the study finds. For example, nearly two in three Democrats (63%) disagrees with the notion that allowing gays and lesbians to marry legally undermines the traditional family, while just 33% agree. In 2003, Democrats were evenly split on the question. Among independents, growing support for gay marriage has largely paralleled increases among Democrats. At the same time, Republican attitudes are little changed. In 2003, 59% of Republicans said homosexuality should be discouraged; today that figure is 54%, according to Pew's polling. The percentage of Republicans who favor gay marriage stands at 27% today, versus 21% a decade ago. There is a gender gap on gay marriage (women are in favor; men are opposed), as well as an age divide. Those over 50 are against gay marriage, with resistance highest among those over 65. Americans with a high school education or less are opposed, while support for gay marriage is highest among college graduates. Income levels, too, reflect differences of opinion; those with family incomes above $75,000 support gay marriage, while those who earn less are evenly split. Regionally, support for gay marriage is highest in the Northeast and the West, while opposition is highest in the South. The Midwest is more evenly divided, with those favoring gay marriage slightly outnumbering opponents (48% to 43%), according to the Pew survey. Among religious groups, only white mainline Protestants have registered substantial changes on gay issues, the study finds. A majority in 2003 (58%) said gay marriage would go against their religious beliefs; today that figure is 44%. Evangelical Protestants remain strongly opposed to gay marriage, while the highest level of support is among those who list their religious preference as unaffiliated. For students of polling, the Pew study offers an instructive look at the ways that the wording of survey questions can generate seemingly divergent results on the same issue. Compared with the ABC/Post survey, the Pew poll found significantly lower support overall, even though the two polls were conducted within a few days of each other. Nor were the differences some sampling glitch. The way that Post/ABC pollsters ask Americans about gay marriage has consistently produced a balance of opinion more favorable to legalization than Pew's polls. Those polled by the Post and ABC News are offered a simple choice: "Do you think it should be legal or illegal for gay and lesbian couples to get married?" Pew asks a more complicated question: "Do you strongly favor, favor, oppose, or strongly oppose allowing gays and lesbians to marry legally?" Pew's results reflect a much closer division of opinion on the issue (a 5-percentage-point difference in favor of gay marriage, versus a 32-point pro-marriage tilt in the latest Post/ABC survey). But, as the Pew study notes, "the two polls tell the same story: significant growth in support for same-sex marriage over the last 10 years."