Garret Jones and I have had an exchange of remarks on twitter: In this exchange, Garret Jones makes three points: Hereditarians/pro-IQ types are not willing to admit to the fact that the private returns to IQ are “low”. (probably false) A substantial fraction of the relationship between national IQ and GDP per capita is due to externalities, not private differences. (true)
The best answer to Garrett would have been to send him this link https://humanvarieties.org/2016/01/31/iq-and-permanent-income-sizing-up-the-iq-paradox/
And see just how he reacts...
And additionally sending him Marks (2022) paper along with this line: "a one standard deviation difference in ability is associated with a about a 40% increase in average personal income for ages 25 to 39." From Cognitive ability has powerful, widespread and robust effects on social stratification: Evidence from the 1979 and 1997 US National Longitudinal Surveys of Youth
A few comments otherwise. Income has its highest predictive power when measured at around age 40 or close to 40. Especially averaged over multiple years near age 40. Averaging attenuates measurement error. Dalliard also made this argument to say that Garrett underestimated the effect of individual's IQ. Another advantage is that when averaged over a large period of time, e.g., income averaged for age 35-44, is that if you want to remove zeros, the interpretation is different and more meaningful. A zero when income is a single-year measure of income can simply mean the individual is still seeking a job and might be earning an income next year, despite not earning any income in this current year. But a zero when income is averaged over so many years implies this person is likely never going to seek a job, and this means removing this zero has less chance of removing a person who is seeking a job.
I read Garett Jones' book "Hive Mind". The entire thesis of the book is that the nation's IQ matters a lot. More than your own. Combine this thesis with Charles Murray's "The Bell Curve", and we're getting somewhere. Higher average IQ means a decrease in a lot of social problems. From crime to violence to drug use to single motherhood.
Is he trying to de-emphasize these positive benefits as somehow being "external" to individual IQ when it comes to GDP growth?
Thought experiment: How much higher would California's GDP be if it doesn't have to spend money on social problems related to low IQ? Rampant drug use, robberies and shoplifting, welfare for single mothers, more money spend on remedial education rather than gifted education, etc, etc etc?
The second point seems a bit Straussian coming from him, given that he has now written two books about average IQ being the source of the "externality".
Aren't there personal cases that low national IQ is beneficial? For example, let's compare 120 IQ person in Nigeria with 120 IQ person in Japan. The first is at the end of the demand curve. He is not under the pressure of competitive conditions like the latter. I think the income-IQ correlation is higher in low IQ countries.