▁O E CD ▁average , ▁and ▁until ▁ 2 0 0 5 ▁have ▁been ▁decl ining . ▁ ▁How ▁much ▁tax ▁policy ▁change ▁over ▁the ▁last ▁thirty ▁years ▁has ▁contributed ▁to ▁income ▁inequality ▁is ▁disput ed . ▁In ▁their ▁compreh ensive ▁ 2 0 1 1 ▁study ▁of ▁income ▁inequality ▁( Tr ends ▁in ▁the ▁Distribution ▁of ▁House hold ▁In come ▁Between ▁ 1 9 7 9 ▁and ▁ 2 0 0 7 ), ▁the ▁C BO ▁found ▁that , ▁ ▁The ▁top ▁fifth ▁of ▁the ▁population ▁saw ▁a ▁ 1 0 - percent age - point ▁increase ▁in ▁their ▁share ▁of ▁after - tax ▁income . ▁Most ▁of ▁that ▁growth ▁went ▁to ▁the ▁top ▁ 1 ▁percent ▁of ▁the ▁population . ▁All ▁other ▁groups ▁saw ▁their ▁shares ▁decl ine ▁by ▁ 2 ▁to ▁ 3 ▁percentage ▁points . ▁In ▁ 2 0 0 7 , ▁federal ▁tax es ▁and ▁trans fers ▁reduced ▁the ▁disp ersion ▁of ▁income ▁by ▁ 2 0 ▁percent , ▁but ▁that ▁equal izing ▁effect ▁was ▁larger ▁in ▁ 1 9 7 9 . ▁The ▁share ▁of ▁transfer ▁pay ments ▁to ▁the ▁lowest - in come ▁households ▁decl ined . ▁The ▁overall ▁average ▁federal ▁tax ▁rate ▁fell . ▁ ▁However , ▁a ▁more ▁recent ▁C BO ▁analysis ▁indicates ▁that ▁with ▁changes ▁to ▁ 2 0 1 3 ▁tax ▁law ▁( e . g ., ▁the ▁exp iration ▁of ▁the ▁ 2 0 0 1 - 2 0 0 3 ▁Bush ▁tax ▁cut s ▁for ▁top ▁ear ners ▁and ▁the