No test measures intelligence. A test only measures you relative to the persons that wrote the test. – loosely quoting Asimov.
2007 is ancient history now. It is an interesting graph that one might correlate with a lack of meritocratic structure in society, but I’m on the low end cause I say this without looking up and reading the study. Pretty pictures evoke emotional blabbering bias and all that.
wealthy families, buy thier children nice private schools, private tutors, Nepotism, and other resources unavailable to othters, also gives them a sense of entitlement, thats why alot of these expensive college produce elitist graduates.