The idea is that if the global hereditarian hypothesis is true to a signi cant degree, for instance 50% of the di erences in national IQs is due to genetic factors, then persons who travel to other countries should be similar in their IQ to their home country, everything else equal (e.g. no selective migration and IQ-environment interaction e ects). Since IQ is a known predictor and cause of many social and economic variables at the personal level, it should also be a predictor at the group level inside host countries. We call this hypothesis "the spatial transferability hypothesis". Many countries now have large and growing immigrant population which make it possible to test this hypothesis.
We have already shown this to be a fruitful idea in multiple datasets (from Denmark, Norway and U.S.). We want to expand to more countries. This however means that we need to acquire datasets from these countries, and often these can only be found or only found easily if one speaks the local language.