The Washington PostDemocracy Dies in Darkness

Whatever the Supreme Court decides, these nine charts show gay marriage is winning

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Today, the Supreme Court opens two days of oral arguments on whether the right to marriage extends to same-sex couples. Both cases—one on California's Prop 8, the other on the federal Defense of Marriage Act—are being closely watched. People began lining up outside the Supreme Court last Thursday to assure themselves a seat.

At the same time, national trends suggest that the fight over gay marriage is coming to an end—no matter what the Supreme Court decides. Here's a look at where the debate stands now, in maps and charts.

A Washington Post-ABC News poll last week found 58 percent of Americans believe it should be legal for gay and lesbian couples to marry, an all-time high since 2004.

"Public attitudes toward gay marriage are a mirror image of what they were a decade ago: in 2003, 37 percent favored gay nuptials, and 55 percent opposed them," Jon Cohen captions. Since 2009, supporters of same-sex marriage have outnumbered opponents. So, what's changing?

Support for gay marriage has grown across demographics—but fastest among Millennials. Back in 2003, 51 percent of Millennials supported same-sex marriage in an annual poll by the Pew Forum on Religion and Public Life. That number has since jumped 19 percentage points to 70 percent in 2013.

Other demographics tracked in Pew polling data have seen smaller increases. The one demographic that does not show any change in the Pew data is Generation X.

Support has increased across religious and racial lines, too, although at different rates.pew 2

Most Americans say they know a relative, co-worker or friend who is gay or lesbian—a 30-percentage point jump from where things stood in 1992.

More awareness of gay and lesbian Americans correlates with a higher level of acceptance of homosexuality.

There are nine states where gay marriage is (or soon will be) legal. 

Massachusetts became the first state to legalize gay marriage in 2003, when its state supreme court ruled in favor of the right. Over the course of a decade, eight other states have followed.

Canada, alongside many European countries, has already legalized same-sex marriage. 

The Netherlands, in 2000, was the first country to legalize gay marriage, followed by Belgium in 2003 and Spain and Canada in 2005. Taken together there, are now 11 countries that allow same-sex marriage.

Overturning Prop 8 could nearly double the population living in states that allow same-sex marriage.

Currently, 15.8 percent of Americans live in a state where gay marriage is legal. If the Supreme Court were to overturn California's Prop 8, the number would grow to 27.9 percent, according to data compiled by the Human Rights Campaign.