Phillips' economic conclusions about the inefficiency of slavery were challenged by [[Robert Fogel]] in the 1960s, who argued that slavery was both efficient and profitable as long as the price of cotton was high enough. In turn Fogel came under sharp attack. | Phillips' economic conclusions about the inefficiency of slavery were challenged by [[Robert Fogel]] in the 1960s, who argued that slavery was both efficient and profitable as long as the price of cotton was high enough. In turn Fogel came under sharp attack. |