Tesla (NASDAQ:TSLA) has been trading at massive volumes since the EV automaker announced it would be included in the S&P500 index on December 21. Retail investors who are long on the stock seem to be doubling down on their investments in TSLA while fund managers try to buy enough stock before the EV automaker’s official S&P 500 inclusion.

According to Refinitiv, traders bought and sold TSLA stock at an average of about $26 billion per session since the company announced its impending S&P 500 inclusion last Tuesday. Tesla stock’s massive trading volumes made up 8% of all stock exchanges in the United States for the past week. Reuters calculated that Tesla’s value of trades surpassed Amazon and Apple’s combined over the same period. 

Tesla now boasts a market cap of $544 billion, helping Elon Musk surpass Bill Gates in net worth. On Wednesday, TSLA rose by 3% and closed at $574. Tesla stock is up by 40% since November 16 when it was revealed that the company would join the S&P500. 

“It’s been crazy. Since Tesla’s (announced) inclusion in the S&P, you’ve had a lot of managers out there that didn’t own enough of it having to buy more,” said the managing director of trading at Wedbush Securities in Los Angeles, Sahak Manuelian. He also stated that retail investors significantly contributed to Tesla’s massive trading volume through apps like Robinhood. 

At the rate TSLA stock has been surging, it could be the sixth most valuable company in the S&P 500 once it joins the index. Tesla’s entry into the S&P 500 was prefaced by the company’s five consecutive profitable quarters. Tesla stock is up by over 400% in 2020 so far, making it the world’s largest automaker by market cap.

Disclosure: I am long TSLA.