For more numerous and granular data points, Eurostat doesn’t seem to measure this below country level, however US Census does. At least, I can easily find maps

For more numerous and granular data points, Eurostat doesn’t seem to measure this below country level, however US Census does. At least, I can easily find maps and papers which use that reference, but not the exact data table quickly. I know I had to grep and visual grep IPUMS dumps with similar projects before. In the meanwhile, I’m biased to buy the hypothesis and have reasonable trust in the studies Caplan quoted, but a graph would be properly convincing.