Amazon.com shares have been on an unstoppable run since the beginning of 2015, surging by 170 percent and adding almost $250 billion to the company's stock market value.
And recently, short sellers are showing a record amount of short interest in the stock, according to a report on Thursday from financial analytics firm S3 Partners.
The amount of investor dollars betting that Amazon shares are headed south jumped to $5.3 billion this week, the first time that number has ever eclipsed $5 billion, according to the report. Short selling averaged $2 billion to $3 billion between 2012 and 2015 and topped $4 billion on three occasions since the middle of last year.
Shares of the e-commerce company hit a record high of $844.36 on Oct. 5 and are up nearly 23 percent this year. Bullishness around the stock has been driven by strong performance in the company's Amazon Web Services cloud division, new services launched including a standalone music streaming service to compete with Spotify and Apple Music, as well as plans to hire 120,000 seasonal workers, a 20 percent rise from 2015.
The chart below, from S3 Partners, shows the spike in short interest relative to the increase in Amazon's stock.