Slight note about Dan Wang picking 2005: That was the peak of CS degrees awarded because it's 4/5 years after the height of the dot-com bubble. So the upward bump in the mid-2000's is somewhat explainable as an anomaly. I think his point 1 is underrated. CS degrees are flat because aptitude is flat. You can compare CS degrees to other degrees over time at nsf.gov: https://www.nsf.gov/statistics/2016/nsb20161/#/report…
Re: the Wordsum test, I can't believe it is seriously used to assess IQ. If we assume that all participants know all of the words used, then maybe it would have some merit. But so many of the words used are either archaic, little-used, or culturally specific to North America that you could only reasonably expect a well-read and/or well-educated (and therefore wealthy) American person to know them.
The only point about this test is it's specific to native speakers of English, but if you were born in North America than it surely applies to you even if your parents speak another language.