8 ) ▁finds ▁that ▁Williams ' s ▁claims ▁regarding ▁the ▁Indust rial ▁Revolution ▁are ▁ex agger ated , ▁as ▁prof its ▁from ▁the ▁slave ▁trade ▁amount ed ▁to ▁less ▁than ▁ 1 % ▁of ▁domestic ▁invest ment ▁in ▁Britain . ▁Richard son ▁further ▁challeng es ▁claims ▁( by ▁African ▁sch ol ars ) ▁that ▁the ▁slave ▁trade ▁caused ▁w ides p read ▁dep op ulation ▁and ▁economic ▁dist ress ▁in ▁Africa ▁but ▁that ▁it ▁caused ▁the ▁" under development " ▁of ▁Africa . ▁Ad m itting ▁the ▁hor rible ▁suffering ▁of ▁slaves , ▁he ▁notes ▁that ▁many ▁Afr icans ▁benef ited ▁directly ▁because ▁the ▁first ▁stage ▁of ▁the ▁trade ▁was ▁always ▁firm ly ▁in ▁the ▁hands ▁of ▁Afr icans . ▁European ▁slave ▁ships ▁waited ▁at ▁ports ▁to ▁purchase ▁cargo es ▁of ▁people ▁who ▁were ▁captured ▁in ▁the ▁hinter land ▁by ▁African ▁deal ers ▁and ▁trib al ▁leaders . ▁Richard son ▁finds ▁that ▁the ▁" ter ms ▁of ▁trade " ▁( how ▁much ▁the ▁ship ▁own ers ▁paid ▁for ▁the ▁slave ▁cargo ) ▁moved ▁heavily ▁in ▁favour ▁of ▁the ▁Afr icans ▁after ▁about ▁ 1 7 5 0 . ▁That ▁is , ▁ind igen ous ▁el ites ▁inside ▁West ▁and ▁Central ▁Africa ▁made ▁large ▁and ▁growing ▁prof its ▁from ▁sla very , ▁thus ▁increasing ▁their ▁wealth ▁and ▁power . ▁ ▁Econom ic ▁historian ▁Stanley ▁Eng erman ▁finds ▁that ▁even ▁without ▁subtract ing ▁the ▁associated ▁costs ▁of ▁the ▁slave ▁trade ▁( sh ipping ▁costs , ▁slave ▁mort ality , ▁mort ality ▁of ▁British ▁people ▁in