The most recent short interest data has been released by the NASDAQ for the 06/15/2015 settlement date, which shows a 355,726 share increase in total short interest for Rigel Pharmaceuticals Inc ( RIGL), to 2,855,027, an increase of 14.23% since 05/29/2015. Total short interest is just one way to look at short data; another metric that we here at Dividend Channel find particularly useful is the "days to cover" metric because it considers both the total shares short and the average daily volume of shares traded. The number of shares short is then compared to the average daily volume, in order to calculate the total number of trading days (at the average volume) it would take to close out all of the open short positions if every share traded represented a short position being closed. Average daily volume for RIGL at the 06/15/2015 settlement decreased to 517,181, as compared to 798,340 at the 05/29/2015 report. That brought "days to cover" up to 5.52, a 76.33% increase from the 3.13 days to cover calculated at the previous short interest data release.The below chart shows the historical "days to cover" for RIGL at previous short interest release dates: An increased "days to cover" value could indicate that short sellers are using the stock to hedge a long bet elsewhere, or could also mean that short sellers believe the stock will decline in price. 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. So investors tend to keep an eye on that "days to cover" metric, because a high value could predict a sharper price increase should the company put out some unexpectedly good news — short sellers might then rush to cover their positions, and if the "days to cover" number is high, it would then be more difficult to close those positions without sending the stock higher (until the higher price produces enough sellers to generate the necessary volume the short sellers need to close their positions).