Yeah these comparisons are typically done incorrectly, as you note. Although Gladwell is often wrong, in this case he happens to agree with most research on the

Yeah these comparisons are typically done incorrectly, as you note. Although Gladwell is often wrong, in this case he happens to agree with most research on the subject, in that the effects are small if at all present. However, it's worth noting that doing a study properly is difficult and there are issues with every single one, so we can't really be too confident of the result. A similar argument shows that the "$2.3 million" benefit of college over high school is vastly overstated, although there is actually some effect in this case.