История изменений

И? где там «пруф» конкретно?

Fogel wrote that small farms were just as productive as free farms. He said that the large plantation-style slave farms (16+ slaves) were the most efficient, having a Total Factor Productivity ratio (Ai/Aj) to be around 1.33. Fogel also wrote that if slaves had a day of rest, they tended to be more efficient because of the extra day of rest. They would be able to regain their energy and thus have more energy to produce more. «In their revised view slaves were hard working; slave labor was of superior quality. Indeed, this helps explain why large slave plantations were much more efficient than free southern farms.»[3] In addition, since different crops were grown in the South and the North, he noted that although slavery was efficient in the South, it would not have been so in the North due to different weather and other conditions.
...
Fogel and Engerman asserted that slavery had a reciprocal economic benefit for slave owners and slaves. They wrote, «Slave owners expropriated far less than generally presumed, and over the course of a lifetime a slave field hand received approximately ninety percent of the income produced.»(p. 5-6) They were estimating the value of housing, clothing, food and other benefits received by the slaves and argued that they lived as well in material terms as did free urban laborers; life was difficult for both classes.[3]

И? где там «пруф» конкретно?

Fogel wrote that small farms were just as productive as free farms. He said that the large plantation-style slave farms (16+ slaves) were the most efficient, having a Total Factor Productivity ratio (Ai/Aj) to be around 1.33. Fogel also wrote that if slaves had a day of rest, they tended to be more efficient because of the extra day of rest. They would be able to regain their energy and thus have more energy to produce more. «In their revised view slaves were hard working; slave labor was of superior quality. Indeed, this helps explain why large slave plantations were much more efficient than free southern farms.»[3] In addition, since different crops were grown in the South and the North, he noted that although slavery was efficient in the South, it would not have been so in the North due to different weather and other conditions.
...
Fogel and Engerman asserted that slavery had a reciprocal economic benefit for slave owners and slaves. They wrote, "lave owners expropriated far less than generally presumed, and over the course of a lifetime a slave field hand received approximately ninety percent of the income produced."(p. 5-6) They were estimating the value of housing, clothing, food and other benefits received by the slaves and argued that they lived as well in material terms as did free urban laborers; life was difficult for both classes.[3]