Tesla (TSLA) , an appealing target for traders looking to profit off the stock's volatility, was once the most-shorted stock on the market. But that's not the case anymore.

As of this week, both Apple (AAPL) and Amazon (AMZN) have surged ahead of the embattled carmaker in terms of short interest.

According to the financial analytics firm S3 Partners, Apple had the highest short interest as of Sept. 12, with $10.518 billion in short interest. Amazon was second at $9.601 billion and Tesla ranked third at $9.522 billion.

"Tesla's short interest was relatively flat for the year and down in the third and fourth quarters, but it was really Amazon's and Apple's surge in short interest which changed the league tables," Ihor Dusaniwsky, S3's head of research, told TheStreet.

During the second and third quarters, short interest in Apple is up 49.2% and for Amazon, it's up 32.1%. Tesla short interest, meanwhile, is down slightly over the same period, dropping 1.23%.

In Tesla's case, short selling activity spiked in early August, around the time that CEO Elon Musk famously wrote on Twitter that he had "funding secured" for a go-private transaction that ultimately fizzled out. Musk has often raged against short sellers as the source of all ills at Tesla, making jokes and lobbing taunts and grievances against short sellers -- collectively, and even on an individual basis

None of that has done much to drive away short sellers, with short interest in Tesla remaining relatively flat throughout 2018, Dusaniwsky noted. Instead, a surge in short interest in Apple and Amazon since early August has led to the two tech giants surpassing Tesla's total short interest as the share prices of both companies have continued to climb. Apple and Amazon are the two most-valuable public companies in the world, with market capitalizations of about $1.09 trillion and $969 billion, respectively.  

S3's tracking helps to illustrate the complexities of short selling, even with regards to high-growth stocks -- like Amazon and Apple -- that are not known for wild bouts of volatility. Since the beginning of the year, Apple's stock is up 28% and Amazon's is up 67%.

But the surge in short selling activity indicates that at least some investors are betting that Amazon's and Apple's rallies will cool off. 

"It is not just the disparate change in the three stocks' share price that moved the needle -- shorts were actively selling into AMZN's and AAPL's rallies while covering shorts during TSLA's price weakness," Dusaniwsky added. 

Apple and Amazon are holdings in Jim Cramer's Action Alerts PLUS member club. Want to be alerted before Jim Cramer buys or sells AAPL or AMZN? Learn more now.

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