The footwear industry market share numbers for May are out, and they tell the story of the ongoing Adidas comeback in America.

According to data from retail researcher NPD Group, Nike’s share of the US athletic footwear market was 34.7% last month, a dip from 35.9% in May 2016. Jordan Brand, the Nike-owned basketball sneaker line, had 11.8% share, a dip from 14.8% in May 2016. Adidas? Its share nearly doubled year over year, from 6.3% in May 2016 to 11.3% in May 2017.

(In case you’re wondering the next four by market share, it goes: Skechers with 6.3%; New Balance with 3.7%; Nike-owned Converse with 3.6%; and Under Armour at 2.4%.)

What else happened in May? Nike’s overall sneaker sales dipped a couple percentage points. Under Armour’s sneaker sales dropped 19%. Adidas’s sneaker sales rose 74%.

And in April, Adidas hit a record-high 13% share of this market and came in at No. 2, topping Jordan Brand for the first time in years. (Why did Adidas tick down from April to May? Market fluctuates from month to month, and it’s a zero-sum game where one brand’s rise means a dip for others; you basically can’t fairly compare share from month to month, only year over year.)

To be sure, Nike is still the top sports apparel dog in America. It sells more shoes in the US than Adidas, plain and simple. (In 2016, Adidas had $3.6 billion in US revenue, a 24% gain; Nike did more than three times that much.) But after a bad run of declining market share in the US from 2011 to 2015, Adidas is now steadily eating away at Nike’s dominance. The three stripes is the hottest brand among sneakerheads, Nike has cooled off, and Under Armour is flailing.

It’s about casual sportswear

The biggest reason Adidas is on the rise is because of an industry trend that benefits the brand: casual sportswear. That refers to both apparel and sneakers, and Adidas has always been known for streetwear, or as the category is called these days, “athleisure.” It’s a trend many bemoan (including Under Armour CEO Kevin Plank), but a trend that hasn’t gone away.

In May, the top five “casual athletic” footwear brands (sporty shoes worn for everyday fashion) did not even include Nike. The top five by market share were Adidas at 23% (a gain of 209% over the same period last year), Skechers at 20% (a 39% bump), Converse at 12% (flat), Sperry at 4% and Keds at 2%.

The stock has responded. Adidas shares are up 22% in 2017 so far, while Under Armour shares are down by the same amount. Nike shares are flat.

There’s another factor at play in Adidas’s recent run: Kanye West.

Adidas first partnered with the rapper in 2014 on a Yeezy line of sneakers and apparel, and last year it extended him to an extensive long-term deal that involves brick-and-mortar shops and, undoubtedly, a lot more money. Many, many sneakerheads insist that West is single-handedly to thank for the Adidas comeback in the States. But NPD Group’s Matt Powell disagrees, and as he likes to point out (and argue about with West fans on Twitter), Adidas only ever releases Yeezy shoes in tiny supply, so there’s no sales data that directly proves West’s influence.

Kanye’s impact on Adidas buzz in America is the hottest debate in the sneaker world.

“Kanye Effect” or not, fashion is Adidas’s sweet spot, and for a period of time that was a weakness—now it’s a strength. The current sports-casual trend means glory days for the German giant. And it means Under Armour has to scramble to catch up. “They needed to make the pivot to sportswear much sooner than they did,” says Powell. “And that’s a hard shift to make, but it’s not impossible.”

Adidas is prioritizing wisely

Here’s just one example of Adidas reordering its priorities in America for the better. In 2015, when Adidas’s 11-year jersey sponsorship of the NBA was coming to an end, the brand chose not to even bid for the new contract. After all, it had spent $400 million for the deal and didn’t have much to show for it at the end: still less than 5% market share in basketball shoes. So it bowed out and let Nike have it (and arguably, overpay for it). Nike spent a reported $1 billion for the new contract, which is only for 8 years.

Having its logo on NBA jerseys didn’t do much for Adidas, so it exited. And it exited at just the time when performance basketball sneakers are in decline anyway: the category is down 23% this year so far. Kids aren’t buying basketball sneakers anymore because they aren’t wearing basketball sneakers for everyday fashion. (That role goes to running shoes these days, but overall, “There is not a single performance category that is trending positively right now,” Powell says. “We are 100% in an athletic fashion trend.”)

Mark King, the US CEO of Adidas, says it’s about picking and choosing the right moves in the NBA, rather than overspending on one big contract. “Is any one thing a catalyst for success? No,” he says. “It’s a combination of doing a lot of right things. Having the NBA doesn’t hurt you, but what we’ve seen is that having it also doesn’t guarantee it will help you. We’ve walked away from the NBA in terms of league sponsorship, but not from a player standpoint. We still love the NBA. We’re not doing as well in basketball as we need to, but we believe that 2018 will be a great year for us, because of the [Adidas-sponsored Houston Rockets star James] Harden Effect and new product.”

That last part is the key: new product. It’s Adidas’s product that has made it cool again in the eyes of American kids and sneakerheads. And if it can keep the product pipeline fresh, that market share number will keep ticking up.

—

Daniel Roberts is the sports business writer at Yahoo Finance. Follow him on Twitter at @readDanwrite.

Read more:

Adidas blows investors away with stellar 2017 outlook

3 big reasons Under Armour has cooled off

Adidas is Yahoo Finance sports business of the year for 2016

Adidas enters uncharted territory, going all in on Kanye West

Why the market likes Adidas’s choice of new CEO