WIG20lev 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 WIG20lev. The historical values were recalculated since December 31, 2005 (the base date). The initial value of WIG20lev index was 2654,65 points and equaled the WIG20 closing value on the base date. WIG20lev changes in the same direction as WIG20 albeit with twice the magnitude, e.g. a 1% rise in the blue chip index will mean a 2% gain in WIG20lev.