It is simply public daily data taken from the website http://regsho.finra.org/FORFshvol20120301.txt and entered into an excel spreadsheet for easy viewing. for example the entry for yesterday Mar 26 Date|Symbol|ShortVolume|ShortExemptVolume|TotalVolume|Market 20120326|ACTC|1075806|0|5889728|O date: 20120326 ShortVolume:1,075,806 TotalVolume:5,889,728 ShortVolume % vs Total Volume: [(1,075,806)/(5,889,728)]x100 = 18%