After the Vietnam war experiment "Project 100,000" (aka McNamara's Morons) the IQ level 80 (9 percentile) became the floor for acceptance in Army. https://www.amazon.com/McNamaras-Folly-Hamilton-Gregory/dp/1...

About 10% of people are too cognitively challenged to positively contribute in the US Army even in the least mentally challenging roles.

At 80 - 85 IQ level person can typically read basic level. They gradate from schools and comprehend simple texts and sentences but may struggle with more complex language structures, vocabulary, and abstract concepts. People with reading disorders or other disorders should not be confused with low IQ.

No, it probably should be higher given how complex even bog standard infantry roles have become.

You’re overlooking a hidden pernicious effect, that IQ is a relative measure that does not identify a declining trend very effectively, i.e., any identified decline in IQ is both a momentary and transient indicator as the norm, i.e., 100 IQ, integrated; and the 100 IQ norm also does not say anything about the overall relative state to any other previous state.

In other words, this is how we end up with Idiocracy where a low IQ person becomes the smartest person in the world right under everyone’s nose.

IQ hasn’t declined though. The Flynn effect means that the median IQ has gone up steadily every decade since they started measuring. It’s unclear why. Maybe better nutrition, better schooling, less leaded petrol - hard to tell.

So an 85 IQ person today is substantially more intelligent than an 85 IQ person in the Vietnam war. That said, the modern infantry man’s job is more complex. I would postulate that the job’s complexity has grown to keep pace with the Flynn effect.

Sadly not. The Flynn effect appears to be obsolete. In many countries it stopped in the 90s and IQs have actually gone down a bit since then. Example:

https://en.wikipedia.org/wiki/Flynn_effect#/media/File:Sunde...

For others interested, this doesn't seem to be fully accepted. A few studies in EU countries (and Australia)) have shown slight regressions from past increases.

No studies done in the US which is the cohort here.

Studies have been done in the US. Here [1] is (to my knowledge) the latest, and it does indeed show a substantial reversal of the Flynn Effect. And to my knowledge the reversal of the Flynn Effect is indeed globally acknowledged. The debate at this point is on the cause.

The main reason early studies were in places like Scandinavia is that they have compulsory military enlistment alongside IQ tests, whose results are made available for research. Studies in places like the US came later, because simply getting a representative and comparable sample is non-trivial. There's also the cultural issue that studies on IQ are walking on eggshells in the US.

And it's not slight regressions. We've gone from gradually and consistently gaining IQ, to the current scenario where some studies [2] have shown declines as great as .29 standard deviation per decade. Meaning in 40 years we'd all be a whole standard deviation away from where the mean used to be. That is exceptionally disconcerting, particularly if it doesn't just flat-line at some point.

[1] - https://www.sciencedirect.com/science/article/pii/S016028962...

[2] - https://www.sciencedirect.com/science/article/abs/pii/S01602...