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.
Same and to include genius IQ
Actually it should show net wealth, not income, as the truly wealthy avoid income tax by taking out loans on their (appreciating) assets. The loans have a very low interest rate, much lower than their assets appreciate, so they are always ahead and can pay off the loans with more loans. The wealthiest people don’t really have jobs or need jobs for income, they use jobs for power and manipulation.