A serf in the Middle Ages was usually reasonably well cared for by his lord. For instance, many, if not most, had access to free medical care, such as it was, as the lord didn't want to lose his property. With the dawn of the Industrial Age, that all went away as the factory owner had no investment in his workers and they were easily replaceable. The life of those workers was, generally, much worse than their predecessor serfs.
Today, H1-B visas are about the same phenomenon. Make workers a disposable commodity and the riches you accrue will be without limit. But all of this overlooks the ascent of robotics, which truly will replace human workers. It will be less effective to throw you shoe in the works when the works just throw it back at you.
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