The most recent short interest data was recently released by the NASDAQ for the 06/15/2015 settlement date, and ARIAD Pharmaceuticals, Inc. ( ARIA) is one of the most shorted stocks of the Russell 3000, based on 15.71 "days to cover" versus the median component at 6.58. There are a number of ways to look at short data, but one metric that we find particularly useful is the "days to cover" because it considers both the total shares short and the average daily volume of shares typically traded. The number of shares short is then divided by the average daily volume, to express the total number of trading days it would take to close out all of the open short positions if every share traded represented a short position being closed.In the case of ARIAD Pharmaceuticals, Inc. ( ARIA), the total short interest at the 06/15/2015 settlement date was 45,350,143 shares, which compares to the average daily trading volume of just 2,886,641 shares, for a "days to cover" ratio of 15.71. When short sellers eventually cover their positions, by definition there must be buying activity because a share that is currently sold short must be purchased to be covered. At the present levels of short interest, if from this point forward every single ARIA share traded represented a short position being closed, then at the average daily volume of 2,886,641 shares it would only be during the 16th trading day that every short position would be closed.