Do migrants bring their human capital with them?

The causes and consequences of cross-national differences in ability.

Written by Noah Carl.

We all know that some countries have more human capital than others. There are large cross-national differences in average cognitive ability, with some countries scoring more than two standard deviations (or 30 IQ points) higher than others. Such differences are not confined to Lynn and Becker’s national IQ dataset; they show up in measures of achievement that have been devised by economists using data from student assessment studies (e.g., PISA). For example, on the World Bank’s measure of harmonized test scores, Niger scores 2.7 standard deviations (or 41 IQ points) lower than Singapore.

They can also be seen in the ranking of countries by number of gold medals at the International Mathematical Olympiad. Tiny Hungary has racked up no less than 85, whereas vast Nigeria has won precisely none.

What explains these large and persistent differences? The default assumption among social scientists is that the overall “quality” of the environment is what matters. Do children have adequate nutrition? Are infectious diseases under control? Is the education system well-funded and well-run? Indeed, performance on the PISA examinations is often interpreted as a simple measure of “school quality”. So if a country ranks high in the PISA tables, it’s assumed that it must have a great education system. Articles are then written on the “secret” of the country’s education system and what other countries can learn from it.

However, growing evidence suggests this can’t be the whole or even the main explanation. Much of that evidence comes from studying migrants.