[Spooky23]

Employees will test the limits with lawsuits. I know at least one large state lost a class action lawsuit due to racial bias on civil service exams.

The problem with comparing IQ results at hire to employment success is that employment outcome is difficult to define over time. You're also unlikely to get statistically relevant data without focusing on large organizations with standardized HR processes. Most of the research is based on supervisory evaluations, which are not the most reliable indicators of anything for a variety of reasons.

The other thing I find amusing is that business folk who talk about this miss the fact that there are large workforces in the US that either have or do use standardized testing like this to hire and promote. Those are government bureaucracies, which function relatively well, but are hardly a model that most folks advocating this would aspire towards.