WIG20short index has been calculated since May 4, 2009. Its values are computed based on the WIG20 index values, so the WIG20 is underlying index for the WIG20short. The historical values were recalculated since December 31, 2005 (the base date). The initial value of WIG20short index was 2654,65 points and equaled the WIG20 closing value on the base date. The movements of WIG20short index reflect the inverse of the WIG20 changes, e.g. a 1% gain of the blue chip index translate into a 1% loss of the WIG20short index.