I wouldn't call IQ a completely useless yardstick. Likely through examining all of the evidence regarding IQ and military performance, the United States governm

I wouldn't call IQ a completely useless yardstick. Likely through examining all of the evidence regarding IQ and military performance, the United States government has come to the conclusion that an IQ below a certain level disqualifies the person for military service. Unsurprisingly, US law is a bit complicated on this, but to summarize, it implies that an IQ below 81 (“tenth percentile”) is disqualifying, and dictates that persons with IQ's between 81 and 93 (“thirty-first percentile”) cannot comprise more than 20% of all enlistees.