How Much Would Open Borders Cost Americans? Steve Sailer quotes an academic study that finds the per-capita income of current U.S. residents would permanently fall by about 40% (forty percent).
This experiment presumes that the only two drivers of national income per capita are national average IQ and an un-explained productivity residual. …
This income decline occurs because cognitive skills matter mostly through externalities: because your nation’s IQ matters so much more than your own, as I claim in 2015’s Hive Mind. Therefore, a decline in a nation’s set of average cognitive skills will tend to reduce the productivity of the nation’s ex-ante citizens.
See World IQ 82, with its big list of national IQs:
The [average IQ] trend is down. Why? Populations are burgeoning in the dumbest countries, but dwindling in the smarter countries. Big government policies encourage smarter women to have careers rather than kids, while dumber woman are subsidized to have kids. The left increasingly imports new voters en masse to the West from dumber countries. It’s hardly rocket science.