I tried to read the study but found it ridiculous. Maybe I’m missing something.
Why would anyone believe that this kind of study would uncover some relationship about “genetics”? What is the relationship between intelligence and obtaining wealth? What is the relationship between your potential intelligence and your ability to achieve your potential due to environment?
Second, 2519 kids sounds like a lot but 20 years is a long time. Was 1950 in Sweden the same as 1970 in Sweden (and then forward because that’s just the period in which the kids were adopted)? What if kids adopted in the 1950’s were raised into a more stable economy? Were the inheritance and gift tax laws the same all the way along? How can one adjust for the incentives to give more to a child as death tax rates go up? (You could examine a large sample and extrapolate but the error potential would be large when applied to a smaller population.)
Third, what if adopted parents specifically avoided selecting children with difficulties that can’t be avoided when you raise your own? This was mentioned in the 538 piece in the context of “random”, but it’s really about whatever bias is in the sample, which means if I were creating a prior for Bayesian analysis, I’d assume the adopted children weren’t randomly selected but were partially selected by parents and partially selected by agencies to fit the adoptive parents’ and the childs’ needs. Lets say you have bright child up for adoption or a baby born to an educated couple of young grad students who can’t raise it: wouldn’t you as an agency look for a family that might bring out this child’s potential? I don’t know, but I assume yes and I know that friends who adopted here specifically chose children born to very bright people (and the birth parents did the same).