Obviously they were "hiring from non-cartel sources" – after all, their staffs grew significantly, at all experience levels, during the no-poach period. Those p

Obviously they were "hiring from non-cartel sources" – after all, their staffs grew significantly, at all experience levels, during the no-poach period. Those people had to come from somewhere else, and I've seen no allegation the cartel coordinated on offers to this large pool of external people. I believe the companies entered the cartel because staff churn is highly-disruptive to ongoing and innovative projects. Churn leaks proprietary info, it deters investment in staff development, it inconveniences or demoralizes those that remain, and it spreads an often-corrosive mercenary attitude. Also, bidding wars for cross-recruited employees will often mean the "winner" suffers the "winner's curse": they are the bidder that erred in overestimating value. And while that delivers a temporary cash bonanza to the employee – "woohoo, this year I'm significantly overpaid!" – it could mean an unsustainability that later hurts their career and lifetime earnings. The best projects and workplaces instead have a strong continuity-of-staff, where firm-specific expertise compounds over time, and teams "gel" to become familiar, highly-effective collaborators. As a result, the welfare of the firm and the employee are not in zero-sum opposition in such matters! Many cartel employees, and especially average employees, may have gained when their workplace stability and productivity was protected from constant poaching. You'd need a lot more study to know for sure. But the law isn't often based on economic analysis, or even domain expertise, but more often on lawyer/legislator superstitions. It's not helpful to think of this as something perpetrated by cartoon villain managers, twirling their mustaches thinking of ways to sneak a few dollars out of their poor, ignorant workers' wallets. It was talented tech managers doing what they thought led to the most sustainable and productive teams, made up of highly-educated and well-informed professionals. Consider: the very middle managers who needed to implement this policy, for their own hires, also knew it applied to themselves as well.