they looked at (1) the economic gains to countries with higher average IQ, (2) the average gains to individuals with higher IQ, and concluded that (3) people with high IQ create vast amounts of positive externality, much more than they capture as individuals
How did they establish that economic gains are influenced by average IQ, rather than both being influenced by some other factor?
How did they establish that economic gains are influenced by average IQ, rather than both being influenced by some other factor?