> Even if everybody had high education, companies would still compete for the best employees. There is no competition for employees because large corporations have agreed to not do so.

Yes, but the degree itself used to be a signal. Of course the school mattered, but getting the degree was considered something. Now the only thing that matters is the school.

> Apple, Google, Intel... discussed no-poach as a way to keep salaries low. Has anything changed?

They wouldn't be able to do that if supply was low. In the 70s-80s, PhDs could incorporate themselves and consult to a very comfortable middle-class living. Nowadays, that's basically impossible for an average PhD. Supply really does matter.