I think you got it the other way around. They have decreased the price of labour and thus increased the demand for it.

This is more or less an employer union.

I don't get your point. As I understand it they have decreased the demand to decrease the price.

It's a approximately a zero sum game in the cartel. That was my point. If the price goes down the demand goes up. So the total demand for programmers increase (the demand for the other companies programmers decrease, of-course).

It's a subjective matter of semantics, though.

I prefer "buyer cartel". It sounds more sinister.

That, along with regulatory enforcement, was basically what broke the collusion scheme. Facebook as a growing company did not want to play ball, and aggressively poached from the other tech companies with bigger offers, forcing them to raise their compensation to retain employees.