New York (CNN Business) This has got to make Tesla CEO Elon Musk happy: In the last seven months, short positions on Tesla shares have lost $8.4 billion, according to S3 Partners, a financial analytics firm.

That's more than the short losses on any other company. The second biggest loss for short sellers came at Apple shares, where they lost just under $6 billion in the same period.

Apple AAPL Tesla TSLA Butis a much larger company and the short positions on it are much, much smaller than those on. Short selling accounts for about 21% of Tesla stock sales currently, compared to about 1% of Apple shares.

Short sellers bet that the price of a stock is likely to go down. If it rises before they can cash out their position, they must buy shares at the higher price to cover their bet. Their losses are theoretically unlimited, and often astronomical.

Tesla shares have been on a run lately, inflicting pain on the the short sellers' positions.