American IQ scores have rapidly dropped, proving the 'Reverse Flynn effect'

This blog post asserts that IQ scores didn't drop for the population as a whole, and that the drop for each individual group is due to changing composition of that group:

https://emilkirkegaard.dk/en/2023/03/new-study-didnt-really-...

For example, if the % of people who do a postgraduate degree goes doubles, it's no longer such a select group, so you'd expect the average IQ of postgraduate degree holders to go down. This doesn't mean IQ scores are going down for the population as a whole.

One more thing: why do so many papers that present charts that show how a mean or median changes over time, without also presenting charts that show how the distribution has changed over time?

It's worth looking up whose blog this is before trusting any of its analysis.

I'd never heard of this person before finding this blog post via Google. So I trust the post as much as I trust any random blog post that seems to make a reasonable argument :)

You trust one of these random people enough to promote it. It's not unreasonable for people to point out that the author is quite infamous for his viewpoints.

It's an ad-hominem (in the original sense of the word: an ad-hominem fallacy is one where the truth or falsity of an argument is determined by the trustworthiness of its proponent rather than by the content of the argument itself).

Is he right? The argument is plausible: the study measures online IQ tests. Certainly in my experience the average person online has gotten dumber in the 30 years I've been on the Internet, because Internet access has expanded and it's now the general population rather than just upper-middle-class academics. But we'd need to see comparisons vs. offline IQ tests, given to a randomly-sampled selection of the population, to be sure.

It's not a fallacy to attack someone's historical reliability in making arguments.