▁ 2 0 % ▁of ▁the ▁labor ▁force ▁in ▁ 1 9 8 3 ▁to ▁about ▁ 1 2 % ▁in ▁ 2 0 0 7 . ▁Class ical ▁and ▁ne oc lass ical ▁econom ists ▁have ▁tradition ally ▁thought ▁that ▁since ▁the ▁chief ▁purpose ▁of ▁a ▁union ▁is ▁to ▁maxim ize ▁the ▁income ▁of ▁its ▁members , ▁a ▁strong ▁but ▁not ▁all - en comp ass ing ▁union ▁movement ▁would ▁lead ▁to ▁increased ▁income ▁inequality . ▁However , ▁given ▁the ▁increase ▁in ▁income ▁inequality ▁of ▁the ▁past ▁few ▁dec ades , ▁either ▁the ▁sign ▁of ▁the ▁effect ▁must ▁be ▁revers ed , ▁or ▁the ▁magnitude ▁of ▁the ▁effect ▁must ▁be ▁small ▁and ▁a ▁much ▁larger ▁oppos ing ▁force ▁has ▁overrid den ▁it . ▁ ▁However , ▁more ▁recently , ▁research ▁has ▁shown ▁that ▁un ions ' ▁ability ▁to ▁reduce ▁income ▁dispar ities ▁among ▁members ▁out we ighed ▁other ▁factors ▁and ▁its ▁net ▁effect ▁has ▁been ▁to ▁reduce ▁nation end al ▁income ▁inequality . ▁The ▁decl ine ▁of ▁un ions ▁has ▁hurt ▁this ▁level ing ▁effect ▁among ▁men , ▁and ▁one ▁econom ist ▁( Ber keley ▁econom ist ▁David ▁Card ) ▁estim ating ▁ ▁about ▁ 1 5 – 2 0 % ▁of ▁the ▁" Gre at ▁D iver gence " ▁among ▁that ▁gender ▁is ▁the ▁result ▁of ▁decl ining ▁union ization . ▁ ▁According ▁to ▁sch ol ars , ▁" As ▁organized ▁labor ' s ▁political ▁power ▁diss ip ates , ▁economic ▁interests ▁in ▁the ▁labor ▁market ▁are ▁dispers ed ▁and ▁policy