ive ▁tax ▁and ▁transfer ▁policies ▁have ▁contributed ▁to ▁greater ▁after - tax ▁income ▁inequality : ▁" As ▁a ▁result ▁of ▁the ▁dimin ishing ▁effect ▁of ▁trans fers ▁and ▁federal ▁tax es , ▁the ▁G ini ▁index ▁for ▁income ▁after ▁trans fers ▁and ▁federal ▁tax es ▁grew ▁by ▁more ▁than ▁the ▁index ▁for ▁market ▁income . ▁Between ▁ 1 9 7 9 ▁and ▁ 2 0 0 7 , ▁the ▁G ini ▁index ▁for ▁market ▁income ▁increased ▁by ▁ 2 3 ▁percent , ▁the ▁index ▁for ▁market ▁income ▁after ▁trans fers ▁increased ▁by ▁ 2 9 ▁percent , ▁and ▁the ▁index ▁for ▁income ▁measured ▁after ▁trans fers ▁and ▁federal ▁tax es ▁increased ▁by ▁ 3 3 ▁percent ." ▁ ▁Tax ▁exp end it ures ▁ ▁Tax ▁exp end it ures ▁( i . e ., ▁exclus ions , ▁dedu ctions , ▁prefer ential ▁tax ▁rates , ▁and ▁tax ▁cred its ) ▁cause ▁reven ues ▁to ▁be ▁much ▁lower ▁than ▁they ▁would ▁otherwise ▁be ▁for ▁any ▁given ▁tax ▁rate ▁structure . ▁The ▁benefits ▁from ▁tax ▁exp end it ures , ▁such ▁as ▁income ▁exclus ions ▁for ▁health care ▁ins urance ▁prem iums ▁paid ▁for ▁by ▁employ ers ▁and ▁tax ▁dedu ctions ▁for ▁mort g age ▁interest , ▁are ▁distributed ▁une ven ly ▁across ▁the ▁income ▁spectrum . ▁They ▁are ▁often ▁what ▁the ▁Congress ▁offers ▁to ▁special ▁interests ▁in ▁exchange ▁for ▁their ▁support . ▁According ▁to ▁a ▁report ▁from ▁the ▁C BO ▁that ▁analyz ed ▁the ▁ 2 0 1 3 ▁data : ▁The ▁top ▁