▁calculation , ▁with ▁most ▁estimates ▁r anging ▁between ▁ 1 1 . 5 ▁million ▁to ▁ 1 5 . 4 ▁million . ▁More ▁recently , ▁John ▁K . ▁Thor nt on ▁has ▁presented ▁an ▁argument ▁closer ▁to ▁that ▁of ▁F age , ▁while ▁Joseph ▁In ik ori , ▁Patrick ▁Mann ing ▁and ▁Nathan ▁N unn ▁have ▁argued ▁that ▁the ▁slave ▁trade ▁had ▁a ▁long - term ▁deb il it ating ▁impact ▁on ▁African ▁economic ▁development . ▁ ▁Mann ing , ▁for ▁example , ▁arrived ▁at ▁the ▁following ▁conclusion , ▁after ▁account ing ▁for ▁regional ▁variations ▁in ▁slave ▁exports ▁and ▁assuming ▁an ▁annual ▁African ▁population ▁growth ▁rate ▁of ▁ 0 . 5 . % : ▁the ▁population ▁of ▁Africa ▁would ▁have ▁been ▁ 1 0 0 ▁million ▁rather ▁than ▁ 5 0 ▁million ▁in ▁ 1 8 5 0 , ▁if ▁not ▁for ▁the ▁combined ▁effects ▁of ▁the ▁external ▁and ▁internal ▁slave ▁tr ades . ▁N unn , ▁in ▁a ▁recent ▁econ ometric ▁analysis ▁of ▁slave - export ing ▁regions ▁in ▁all ▁parts ▁of ▁Africa , ▁found ▁" a ▁robust ▁negative ▁relationship ▁between ▁the ▁number ▁of ▁slaves ▁taken ▁from ▁a ▁country ▁and ▁its ▁subsequent ▁economic ▁development ." ▁N unn ▁arg ues , ▁moreover , ▁that ▁this ▁cannot ▁be ▁explained ▁by ▁pover ty ▁prior ▁to ▁the ▁slave ▁trade , ▁because ▁more ▁dens ely ▁populated ▁and ▁econom ically ▁developed ▁parts ▁of ▁Africa ▁re gress ed ▁behind ▁previously ▁less ▁developed , ▁non - s lave ▁export ing ▁areas ▁during ▁the ▁course ▁of ▁the ▁Atlantic , ▁trans -