And while the traders on r/wallstreetbets—the Reddit forum that kicked off the unlikely rally for GameStop stock—may be racking up profits, the damage is accumulating for short-sellers, the investors and hedge funds who bet against, or “short,” the stock. By Friday, short-sellers had lost $19.75 billion on GameStop so far this month alone, according to S3 Partners, a New York–based firm that tracks short positions on U.S. stocks.

That’s an extraordinary bungle: By comparison, Tesla—a long hated stock that defied bears with its market-crushing performance last year—cost short-sellers some $40.1 billion in all of 2020. (For context, Tesla’s market value is also 37 times that of GameStop.)

The losses have hit hedge funds shorting GameStop including Steve Cohen‘s Point72, as well as other high-profile short-sellers like Andrew Left, who runs Citron Research, a firm that built a reputation for publishing reports on stocks he believed were destined to fall.

After announcing last week that he was shorting GameStop when the stock was trading around $40, Left said Wednesday that he had largely abandoned the trade “at a loss 100%,” covering the short—or buying back the stock—when it reached the $90 range. On Friday morning, Left said he would no longer publish short reports at all, seemingly marking a turning point for the short-selling industry. Instead, he will focus on long, or bullish, investments—stocks he believes will rise—and distribute his research to individual investors.

“We understand the changing dynamics in the market,” Left said in a video released on Twitter Wednesday. “So with that, we’ll become more judicious when it comes to shorting stocks.”

Still, an analysis of short stock positions by S3 Partners shows that short-sellers aren’t done betting against GameStop—and many are just getting started.

“As soon as some shorts are covering there are a line of new short-sellers looking to locate and short GME at these high stock price levels,” says Ihor Dusaniwsky, S3’s managing director of predictive analytics, citing his conversations with brokers. “Much like in trench warfare, after the first wave gets decimated, the second wave takes up the banner and marches onward.”

Indeed, even as GameStop stock multiplied several times over this week, short positions remained “relatively stable,” with a slight 8% decline when a selloff in the stock Thursday (sparked by Robinhood and other brokerages limiting trades) allowed short-sellers to buy back the stock at lower levels, Dusaniwsky says.

Still, GameStop shares sold short currently amount to more than 113% of the company’s total outstanding shares, making it the market’s most shorted stock by that measure, according to S3.

That’s also made shorting GameStop outrageously expensive, and yet investors are paying the price: The borrowing fee to short GameStop stock is now nearly 30%—with the fee rising to 50% for those making new short bets on GameStop. By contrast, the average borrowing fee for shorting U.S. stocks is under 1%, S3 says.

After all, despite the black eye many short-sellers took on GameStop this week, others remain undaunted in making bearish calls.

Nathan Anderson, founder of Hindenburg Research—which made possibly the most famous short call of 2020 in his takedown of Nikola Corp., halving the market cap of the electric-vehicle maker with his report—falls in the latter camp.

“While the guns are turned on short-sellers at the moment,” says Anderson, “I’m encouraged that the right questions are finally being asked. It’s early, but I’m hopeful that it leads to a broader understanding of how the system is flawed. Because that’s the only way it will ever actually improve.”

Additional reporting by Bernhard Warner.