MPLX’s (NYSE:MPLX) short percent of float has fallen 13.8% since its last report. The company recently reported that it has 9.90 million shares sold short, which is 2.81% of all regular shares that are available for trading. Based on its trading volume, it would take traders 4.05 days to cover their short positions on average. Why Short Interest MattersShort interest is the number of shares that have been sold short but have not yet been covered or closed out. Short selling is when a trader sells shares of a company they do not own, with the hope that the price will fall. Traders make money fr…