Last year, all five of the surviving U.S. presidents gathered in Dallas. They were there to dedicate the presidential library of George W. Bush; the show ended up being stolen, however, by the honoree’s father. And, more specifically, by the honoree's father's socks—which poked out from beneath the wheelchair-bound ex-president's pant cuffs, revealing themselves to be a particularly sassy shade of cotton-candy pink.

This wouldn’t be the first time that the elder President Bush would experiment with adventuresome hosiery; George H.W. has also been photographed sporting designs of lavender and orange and varying combinations of red, white, and blue. In that, he has been in good company. The statement sock—whether distinguished by a bright hue or a bold pattern or both at the same time—has become the go-to fashion accessory for guys from Wall Street, where “Friday socks” is a thing, to Silicon Valley, where every day is Friday. (Startup guys, according to one Bay Area buyer, favor not just colorful socks but also socks decorated with “words like ‘bacon’ and ‘beer’” and also “anything with ninjas.”)

All of which helps to explain new sales numbers released today by the retail analytics firm NPD, revealing a 2-percent growth in sock sales between August 2013 and August 2014. That's a rate that has, in a weak economy, outpaced the general growth of the $206.7 billion global apparel market. And NPD speculates that it has been men, in particular, who have driven the increase. As Marshal Cohen, NPD’s chief industry analyst, explains it: “Over the past year, socks have become yet another outlet for expressing the extra splash of pattern and color they seek.”

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The appeal of the statement sock—an answer, perhaps, to the statement jewelry that has long added versatility to women’s wardrobes—has contributed to a somewhat counterintuitive phenomenon: Last year, for the first time in more than a decade, the sales of men's apparel outpaced those for women. Driving the growth, according to the Wall Street Journal? “Double-digit gains in outerwear, pants, and socks.”

In part, to be sure, that increase has been due to sales of athletic socks. In part it’s been due to an increase in the average price of socks, which rose 24 percent between 2011 and 2013 (from $1.76 to $2.18 a pair, according to the NPD Group's Consumer Tracking Service). The other cause, though, has been less about socks as cushion and more about socks as fashion: the appeal of a flash of ankle peeking out from beneath the pant leg of an otherwise hum-drum suit. As the writer Josh Bearman explains it: “Socks are like lingerie for men. Only you know it’s there under your pants, but then when you walk, you give a little peek of what you’ve got on underneath.”

Call it Victor’s secret. Or, um, man-gerie. Or, um, brosiery. Regardless, it's giving the tie and the pocket square a run for their money when it comes to adding pizzazz to guys’ outfits. But the rise of the statement sock also makes you wonder: Why this? Why now? Why did it take so long for socks to become sassy?

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One theory: Europe. Experimentation with gussied-up ankles, NPD’s Marshal Cohen told the Journal last year, started there, and then—like so many Windsor knots and slim-cut pants and spread-collar ginghams, migrated West to the States.

Another, complementary, theory: Nike. “Socks used to be a commodity part of the basketball business, but we developed a new innovative sock," the Nike executive Jayme Martin recently told a group of the company’s investors, referring to the Elite socks that Nike released in 2008 and issued in various colors and prints. At an average cost of $14 to $18 a pair, the Elites form a crucial component of Nike’s annual $100 million in sock sales. And that’s not just because they are, as barriers between shoe and skin, practical. "Kids aren't just wearing them on the courts,” Martin explained. “They are social currency."

That idea—that recognition that socks can be both commodity and currency—encouraged the company to see them, and sell them, as fashion accessories. As Cohen told the Journal: "What Nike Elite did was bring attention to the better-socks business. It's no longer just grabbing white socks out of the drawer. Now it's got to be this sock. The consumer-born trend sparked the whole idea of dressing the foot up."

Which wasn’t, of course, a wholly new idea. Almost since their invention, socks have doubled as decoration. The earliest versions were made of animal skins, gathered and tied around the wearers’ ankles; later versions—like those worn by the ancient Greeks and Romans—were made of matted animal fur. And socks have long been a kind of status symbol. By 1000 AD, socks—which are, given their shape, labor-intensive to produce—had become symbols of wealth among European nobility. They often included elaborate decorations.

A statement sock, made of cotton, from 12th-century Egypt (Wikimedia Commons)

Brosiery continues that tradition. “Socks are a way that I can stand out at work,” Roland Gonzales, who works in finance in New York, explains. “Everyone wears the same sort of conservative uniform,” he says. “This is a way to personalize my work wardrobe.” Rob Kardashian’s line of socks, which he sells at Neiman Marcus, feature messages like “Kiss Me” and “YOLO” on their soles. Sales for these all-too-literal of statement socks tripled in the first six months of business, a success Kardashian attributes to the fact that “everyone is wearing colorful socks.”

An added bonus: Statement socks are an easy and often inexpensive indulgence. Though high-end designs are certainly available (you can buy $185 socks at Barney’s, should your path in life lead to that), you can also buy the socks at stores like Forever 21 and Target, the latter of which says it "has seen a steady interest” in statement socks since introducing them in 2012.

Socks also have also, unsurprisingly, made their way to online retail, where services like Nice Laundry (“the Warby Parker of men’s socks”) sell packs of six pairs with names like "Chief," "Hot Shot," and "Prepster II" for $49 to $59, shipping included. "We make it very easy for you to refresh your entire sock drawer," Ricky Choi, Nice Laundry’s co-founder, told the New York Daily News.

Choi should know: His own sock drawer, he says, has more than 150 pairs.