> There are 10s of thousands of businesses in the US. It's hard to believe there'd be any remotely successful collusion in keeping wages down.

This takes many assumptions: People know of all these businesses. People are able and willing to move at a whim (not so easy with family/friends), people are willing to change their jobs every other month (for a business a job is just a transaction of money vs time, human beings, failed constructions that we are don't see it that simple) and so on. Neither the world nor people are completely rational, so things which work in theory often donThere are 10s of thousands of businesses in the US. It's hard to believe there'd be any remotely successful collusion in keeping wages don't work in reality.