 Other researchers and historians have strongly contested what has come to be referred to as the "Williams thesis" in academia.David Richardson has concluded that the profits from the slave trade amounted to less than 1% of domestic investment in Britain.Economic historian Stanley Engerman finds that even without subtracting the associated costs of the slave trade (e.g., shipping costs, slave mortality, mortality of British people in Africa, defense costs) or reinvestment of profits back into the slave trade, the total profits from the slave trade and of West Indian plantations amounted to less than 5% of the British economy during any year of the Industrial Revolution.