 Critics have also argued that slavery remained profitable in the 1830s because of innovations in agriculture so the profit motive was not central to abolition.Richardson (1998) finds Williams's claims regarding the Industrial Revolution are exaggerated, for profits from the slave trade amounted to less than 1% of domestic investment in Britain.Richardson further challenges claims (by African scholars) that the slave trade caused widespread depopulation and economic distress in Africa—indeed that it caused the "underdevelopment" of Africa.