AMC short sellers are digging in despite a 5-day rally in the stock that's driven billions in losses, data shows

• AMC short sellers borrowed even more shares amid the week-long gains in the stock.
• They've dug in, despite losing more than half a billion dollars on Thursday alone.
• Shares of the theater chain have tripled in price in just five days of trading.

AMC short sellers aren't letting up despite a record five-day rally in the stock. Instead, they're digging in further.

A week ago, the number of AMC shares on loan, used to short the stock, was 124 million. As of Friday, the number of shares on loan was 132 million, new data from ORTEX shows.

That suggests short sellers aren't covering their positions, but instead are going in even further on their view AMC stock will decline. Short interest in the company is 21%, according to MarketBeat data.

In the past week, shares of the world's largest movie theater chain have nearly tripled in price, rising as high as $36.56 in Friday trading - a staggering leap from last Friday's close of $12.08.

"Given the dramatic price increase, it's surprising that we haven't seen much short covering yet," said ORTEX co-founder Peter Hillerberg. "This price action must be very concerning for institutions that are short."

When share prices go up, short sellers get squeezed. They have to cover their positions by becoming buyers, sending the price even higher.

Staying put in their positions while the stock price rises means big losses for short sellers, though.

On Thursday alone, the AMC rally caused short sellers to lose $587 million, according to ORTEX data.

As meme stocks, such as AMC, GameStop, and Virgin Galactic, have rallied overall this week amid positive sentiment among retail traders, short sellers have lost $2.76 billion from Monday through Thursday, the data showed.

AMC's rally began after the chain's largest shareholder sold nearly all of its remaining stake in the company. Private Chinese conglomerate Dalian Wanda Group, which bought the company for $2.6 billion in 2012, now only has a .002% stake in AMC.

Retail traders cheered the opportunity to buy more shares. On Twitter, the hashtags #AMCSTRONG, #AMCAPES, and #AMC500K have all been trending amid this week's gains.