regressive

adjective
1
becoming or making something less advanced
پسرفت کننده, رو به عقب, پس‌رو, پس‌رونده
2
having less effect on the rich than on the poor
ارتجاعی, نزولی, عقب‌رونده, پسرفت‌کننده
A regressive tax structure is one in which the average tax rate falls as income level rises.