▁increased ▁pay roll ▁tax es ▁passed ▁as ▁part ▁of ▁the ▁Aff ord able ▁Care ▁Act ), ▁the ▁effective ▁federal ▁tax ▁rates ▁for ▁the ▁highest ▁ear ning ▁household ▁will ▁increase ▁to ▁levels ▁not ▁seen ▁since ▁ 1 9 7 9 . ▁ ▁According ▁to ▁journalist ▁Tim othy ▁No ah , ▁" you ▁can ' t ▁really ▁demonstrate ▁that ▁U . S . ▁tax ▁policy ▁had ▁a ▁large ▁impact ▁on ▁the ▁three - de cade ▁income ▁inequality ▁tr end ▁one ▁way ▁or ▁the ▁other . ▁The ▁inequality ▁tr end ▁for ▁pre - tax ▁income ▁during ▁this ▁period ▁was ▁much ▁more ▁dram atic ." ▁No ah ▁estimates ▁tax ▁changes ▁account ▁for ▁ 5 % ▁of ▁the ▁Great ▁D iver gence . ▁ ▁But ▁many ▁– ▁such ▁as ▁econom ist ▁Paul ▁K rug man ▁– ▁emphas ize ▁the ▁effect ▁of ▁changes ▁in ▁tax ation ▁– ▁such ▁as ▁the ▁ 2 0 0 1 ▁and ▁ 2 0 0 3 ▁Bush ▁administration ▁tax ▁cut s ▁which ▁cut ▁tax es ▁far ▁more ▁for ▁high - in come ▁households ▁than ▁those ▁below ▁– ▁on ▁increased ▁income ▁inequality . ▁ ▁Part ▁of ▁the ▁growth ▁of ▁income ▁inequality ▁under ▁Republican ▁administr ations ▁( des cribed ▁by ▁Larry ▁Bart els ) ▁has ▁been ▁attributed ▁to ▁tax ▁policy . ▁ ▁A ▁study ▁by ▁Thomas ▁P ik et ty ▁and ▁Em manuel ▁S ae z ▁found ▁that ▁" large ▁redu ctions ▁in ▁tax ▁progress ivity ▁since ▁the ▁ 1 9 6 0 s ▁took ▁place ▁primarily ▁during ▁two ▁periods : ▁the ▁Re agan ▁presiden cy