HERZOGENAURACH, Germany — Adidas AG executives are decidedly happy these days, thanks to Pharrell Williams.

While they were throwing euros at Kanye West and letting him run amok in the design department, the sober heads in Herzogenaurach, Germany, pulled out a 45-year old basketball shoe called the Superstar and put it in Pharrell's hands. Adidas declared 2015 "the year of the Superstar" and in March released 50 color-saturated versions that the soft-spoken pop star touted in rainbow-laced ads.

Adidas designers didn't stop at 50. There were Superstars in metallic gold, red suede and a curry yellow with velcro straps. There were high-top versions and pairs that glow in the dark. People who didn't find a version of Superstars to like could customize one. It was a well-executed example of fashion’s best economics: Take a classic and tweak it.

The result? Adidas just announced that it sold 15 million pairs of Superstars last year, far more than any of its other shoes. In other words, these nondescript kicks from the 1970s have become a billion-dollar business. At $100 or so per pair, they accounted for almost $1 in every $10 Adidas took in last year.

Kanye West may well be king of the special-release sneaker. He is, no doubt, helping Adidas regain some street cred against Nike Inc. But most of the profit in small-batch footwear goes to sneakerheads fortunate to get their hands on a pair and then flip them on secondary markets. Make no mistake: West is playing small ball. All seven of his "Yeezys" to date have sold out "instantly." Meanwhile, he doesn’t come cheap. Tally up the profit and loss, and the Yeezy becomes a marketing exercise more than an immediate moneymaker. Adidas claims to be the most popular sneaker brand on Instagram, thanks, in part, to West.

When it comes to the fashion crowd, he might not even have been Adidas's greatest salesperson last year. That honor arguably went to Phoebe Philo, creative director for Céline, a high-end line of bags and shoes from LVMH Moët Hennessy Louis Vuitton SE, the famed fashion house. At a Paris fashion show in late 2014, Philo casually strolled onto the runway for a victory lap wearing a pair of Stan Smiths, another minimalist Adidas shoe from the 1970s.

This wasn't lost on those who spot trends in streetwear. The kicks already had some momentum that stemmed from a 2013 Vogue shoot with Gisele Bündchen, nude save for footwear. Suddenly, Stan Smiths were ubiquitous on fashion blogs and in the hippest corners of the urban clothing world. They have become to women what Air Jordans were to middle-school boys in the late '80s.

"The last time I was in Paris, it seemed like every woman I saw was wearing the white-and-green Stan Smiths," said Mona Bijoor, founder of JOOR, a digital marketplace connecting brands and retailers. "Last winter, it was Canada Goose [jackets], now it's these Adidas sneakers."

All told, revenue from the Adidas “Originals” line, which includes such vintage stalwarts as Superstar and Stan Smith, surged by 46 percent in the most recent quarter. No other part of the business came close to matching that growth. The company’s soccer gear, tightly hitched to Argentine phenom Lionel Messi, managed a 26 percent gain for the year while its running revenue increased by 6 percent.

Sometimes, being cool is effortless.

By Kyle Stock; editor: Alex Dickinson.