However for many tasks, tasks suitable to stupid people, tasks for bad people, tasks where you want people to reliably do as they are told rather than make good decisions, the sort of tasks that most black people are suitable for, slavery was markedly more productive and efficient than free labor, with the slave producing more value for himself and his owner with less labor, than he did when freed.

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If masters and slaves were better off than employers and employees, an economist would ask, why could they not just cut a deal to do what they previously did, only without chains and beatings, do the same tasks in the same way, only as employees?

The answer is that question is: that the former slaves, once freed, could not credibly commit to stick to such a deal, and generally did not stick to such a deal, thus economically worse off. Stupid people, prone to violence, with short time horizons, needed masters.