And within the West it was in the places without slavery. As countries gave up their colonial slaves, serfs, peasants, etc. they started advancing. The countries that reverted back via fascism and the like saw themselves broken.

A slave works to the point where they are no longer whipped. An employee, in theory at least, is rewarded with higher pay for being more productive. Sometimes I wonder if anyone has researched the industries that pretty much pay everyone the same minimum wage and their output over time. I go to client sites and some of them everyone is paid terribly and the efficiency is staggering low.