One of the correlations he runs looks at the relationship between a state's gross product per capita and its IQ. With an r-value of .28, the correlation trends in the expected direction but is modest.
Because the cost-of-living varies widely between states (and it varies even more so globally between nations), comparisons based on nominal dollar amounts can be misleading (the infamous hoax spurriously estimating average state IQ demonstrates). If only nominal values are considered, simply raising the state's minimum wage will increase its income per capita, but such a move hardly makes the state wealthier.
IQ is related to economics in another, more vigorous way. Steve Sailer created a monetary standard-of-living table awhile back. These values correlate with estimated state IQ at .65 with an infinitesimal P-value (definitely not a fluke). The sparsely populated, cold, and old northern states are relatively expensive by comparison with the rest of the country (logistics costs alone preclude such places from being easily affordable). If the Dakotas and Montana are removed, the correlation jumps to .73.
This is yet another reason raising America's IQ should be a top national priority. We need a merit immigration system that insures that migrants arriving boost the national IQ, instead of pressuring it downward toward Latin American levels. We also need to do away with the regressive nature of the EITC. Instead of phasing it out as income increases, phase it in as income increases.
Crime reduction, better health, reduced infant mortality, greater longevity, and wealth parity are all notable benefits of having a higher average IQ. In the words of Randall Parker:
Anything that could raise average IQ a few points would do more to boost economic growth and lower social pathologies than increased educational spending or the other typical liberal or free market libertarian nostrums.