> One showed that GDP per worker is directly correlated to national IQ. That suggests a strong trend across the entire GDP of countries, not one-off highly specific jobs.
Seems to me it suggests national wealth strongly predicts ability to alleviate the environmental conditions (such as, but not limited to, malnutrition) known to adversely impact IQ.
But that's neither here nor there.
> The second described the growing body of evidence that an IQ test is the single most useful datum you could get about a potential hire.
And if that is really supportable generally, it's probably also easily supportable for a great many specific jobs; where that's the case, IQ tests, regardless of unequal impact on protected classes, are legal, and, as I've said, contrary to your claim of illegality, they've been upheld in a number of cases for just that reason.
> Companies and hiring managers will try to use the best proxies for guessing potential worker productivity they can get.
That's probably less true in practice than you think, though it's the natural expectation of you make a lot of simplifying assumptions.
> Denying them objective data leads to them relying on much less accurate, more subjective, and more biased "wisdom."
Perhaps, but literally nothing but cargo cult “wisdom” is denying them objective information in the form of IQ where they actually empirically is the best tool for the job.