Another unexamined factor may also have contributed to rises in productivity. Slaves were valuable property, and much harder and, thanks to the decline in supply from Africa, costlier to replace than, say, the Irish peasants that the iron-masters imported into south Wales in the 19th century.Slave owners surely had a vested interest in keeping their 'hands' ever fitter and stronger to pick more cotton. Some of the rise in productivity could have come from better treatment. Unlike Mr Thomas, Mr Baptist has not written an objective history of slavery. Almost all the blacks in his book are victims, almost all the whites villains. This is not history; it is advocacy.