Marriage equality is back in the news, as dozens “friend-of-the-court” briefs are arriving at the U.S. Supreme Court in advance of oral arguments in four cases examining whether state bans on same-sex marriage are constitutional.

Among those coming out in favor of a nationwide right to marry are hundreds of iconic American companies including Coca-Cola and PepsiCo, Apple and Google, Delta and United Airlines; General Mills and GE, Morgan Stanley and Goldman Sachs, and even New England Patriots and San Francisco Giants. Some 379 corporations and employer organizations signed an amicus brief.  Another brief was signed by a number of leading Republicans, including major conservative donor David Koch.

Arguments are set for April 28 and a decision is expected by June. This looks like it is the final lap in the historically successful movement that began only a decade ago with Massachusetts being the first state to marry gay couples.

Currently, marriage equality is the law in 37 states, which comprise 70% of the U.S. population. According to a recent CNN poll, 63% of Americans support the right of same-sex couples to marry. That includes a majority in every region of the country, including 57% support in the south.

So why have major corporations waded into the marriage debate? Well, as polls show, the issue isn’t as contentious as it used to be.

Add to those previous figures this fact: 75% of Americans ages 18-34 support same-sex marriage, an increase of 10 points since 2012.  To ZEITGUIDE friend Marc Solomon, national campaign director of advocacy organization Freedom to Marry and author of “Winning Marriage”, that offers even more incentive for businesses to show their support.

“Many companies are focused on being seen as forward-looking, appealing to the best-and-the brightest younger employees and consumers. That’s a major driver behind these companies’ signing this brief: it’s creating a competitive advantage for themselves to show they are a cool, forward-looking company and aligning their values with those of millennials.”

For American businesses, a uniform law on marriage equality across the country also has massive economic benefits.

A 2014 Marsh and McLennan report commissioned by Freedom to Marry found that for American businesses, inconsistent state marriage laws impose a $1.3 billion annual cost. The patchwork landscape creates a general mess for multi-state employers, which have to maintain multiple benefits policies and HR-related systems.

The Williams Institute at UCLA has also been researching the economic impact of same-sex marriage to states. Looking at the last 10 years, what did they find? States that allow same-sex marriages see big benefits. New York City along took in $259 million in new wedding services and travel dollars the first year after passing the Marriage Equality Act.

The report estimates that nationwide marriage equality could produce an economic boost of up to $2.6 billion in the first three years and support 13,000 jobs.

Since the Supreme Court largely gutted the federal Defense of Marriage Act in 2013, 65 state and federal courts have struck down marriage bans. With this momentum, most court-watchers believe it’s all over but the ruling. We can expect marriage equality for all by the end of the Court’s term on June 29. And it won’t just be a victory for civil rights, but a win for the economy as well.