Ugly Christmas sweaters--they're comically ornate, relentlessly tacky, and contemptuous of fashion's most sacred tenets. They're also all the rage.

This holiday season, retailers like Bloomingdale's and H&M are adorning their display windows and catalogs with snowflake and reindeer knits, according to The Wall Street Journal, while thrift stores and websites struggle to keep their vintage designs in stock. Searches for "ugly Christmas sweaters" are 30 percent higher this December than last, the Journal notes, while eBay witnessed its most expensive holiday sweater sale ever this year: $282.59 for a sweater with three reindeer gracing the front.

What accounts for the ugly Christmas sweater's popularity?

  • A Mixture of Nostalgia and Ironic Humor, proposes Rachel Dodes at the Wall Street Journal. The Christmas sweater transitioned from a homespun treasure to a mass-market hit in the 1980s, she explains, and has thrived commercially in part because it conjures up "memories of grandma" and associations with holiday cheer. But one need look no further than the website myuglychristmassweater.com--whose inventory includes a vest decorated with a stuffed-animal reindeer head and battery-powered light-up antlers--to conclude that people are also just having fun with the renegade fashion.
  • Adults Imitating Young People, offers Andrea Simakis at The Cleveland Plain Dealer. While the "modern-day origins of the godawful sweater" can be traced to the "knitted pullovers with clashing colors and Rorschach test patterns" that Bill Cosby wore on The Cosby Show, the Cosby sweater's popularity petered out in the mid- to late-1980s, becoming the "province of dowager aunts, clueless dads and craft-fair-loving grannies." But today, Simakis continues, "the festive, 'made in China' monstrosities are chic again, thanks to high school and college students with a taste for the ironic. And now, as they did with the Honda Element and Facebook, adults have co-opted the trend, throwing their own kitschy sweater soirees for grown-ups."
  • Growing Popularity of Ugly Sweater Parties, submits Nikki Lackowski at Patch's Marinda del Ray, California site. The Christmas sweater has a long history, Lackowski concedes: "There are knitting patterns of snowy pines dating back to the 1950s, the era when the commercialization of Christmas really took off." But it's making a comeback now as people throw contests for the ugliest sweater online or at parties with co-workers or friends.
  • And the Psychology Underlying These Parties, adds Jason Fell at Entrepreneur: "The parties have caught on because the outré attire gives people a chance to let their guard down."
  • Google, posits David Zax at Fast Company. Zax profiles RustyZipper.com, which has sold 3,000 ugly Christmas sweaters this year, and learns that 20 percent of the company's web traffic comes from Google AdWords clicks. This leads Zax to conclude that "the ugly Christmas sweater boom is fueled by Google juice," though Rusty Zipper's Jennifer Chadwick also suggests that Americans are embracing hideous knits as "both a celebration and mockery of holiday excess and Christmas aesthetics."