America’s top three selling beers—Bud Light, Coors Light and Miller Lite—have all seen sales declines this year.

Craft breweries have undoubtedly brought more innovation to our modern beer scene than can be overstated. And yet, in the last half-century, arguably the single most impactful change in the beer world came just before the craft era dawned… the invention of “light beer.”

Originally introduced to the mainstream with Miller Lite in the mid-1970s, light beers have gone on to become, by far, the best-selling beers in America for decades. Currently, the three top beer brands in terms of sales are Bud Light, Coors Light and Miller Lite, in that order. To put things in perspective, last year, Miller Lite, the worst selling of those three beers, still had over ten times the sales of Sierra Nevada Pale Ale. But even though those brands are still holding onto their positions, cracks in their dominance are beginning to show, and even the massive beer companies behind them are starting to worry.

Yesterday, Molson Coors Brewing, who makes Coors Light and Miller Lite in the United States, announced that the company’s U.S. sales-to-retailers volume was down 2.9 percent in the third quarter compared to the same quarter last year, according to the Wall Street Journal, and that sales of its two signature light beer brands were largely to blame. Last month, Bud Light maker Anheuser-Busch InBev presented even worse news, saying its U.S. revenues were down 5.3 percent, leading one analysist to say he “can't remember a quarter as bad,” according to MarketWatch.

The numbers breakdown for light beers tells the tale even more clearly. According to Nielsen data from Beer Marketer’s Insights, sales of Bud Light, Coors Light and Miller Lite are down 5.7 percent, 3.6 percent and 1.6 percent respectively so far this year. Going back to 2010, the light lager category as a whole has seen volumes decline by 14 percent to 65 million barrels in 2016. Again, let’s keep things in perspective: According to the Brewers Association, the entire craft beer sector only produced 24.6 million barrels last year. No one has to start stockpiling light beer before it goes the way of the dinosaur.

Still, light beers have shown such ubiquitous appeal for so long, a decline of this magnitude can’t simply be overlooked or brushed aside. “I think it's safe to say that the industry had a tough summer,” Gavin Hattersley, chief executive of Molson Coors's U.S. business unit MillerCoors, said during this week’s earnings call. Instead, the company searched for silver linings, like how Bud Light is sinking so fast, Coors Light and Miller Lite are actually gaining ground when it comes to market share. “We're very pleased with our performance with Miller Lite, in particular,” Molson Coors CEO Mark Hunter noted. “It's doing well in a declining segment.” Or to put it another way, it’s catching up in a race that fewer people apparently want to be watching.