There is a risk that the brakes could be slammed on Tesla’s astonishing November run when it joins the S&P 500 index on 21 December. Experts believe that last month’s astonishing share price surge may have been powered by a mad dash for Tesla stock by thousands of private investors who hope to flip their shares to tracker funds as they adjust portfolios to reflect the new S&P index entry.

But some market watchers have warned that too much stock may have been snapped up in the buying binge, and that these shares will not easily find new homes at current levels.

Calculations suggest that about 120 million Tesla shares will be needed to satisfy index fund demand when the electric car maker enters the S&P, about 15% of the free float after excluding Musk’s personal 18% stake.

Since the Elon Musk-founded business won a spot in the exclusive index on 17 November, more than 480 million shares have changed hands, sending Tesla’s share price soaring 39% to a record $585.76 on 27 November.

That implies a market value of $538 billion, which would make it the S&P 500’s sixth largest company, ahead of Warren Buffett’s Berkshire Hathaway and Walmart, the world’s biggest retailer, despite being ranked number 367th on earnings.