It tracks rare surnames, so there aren’t many distant cousins to skew the results. The point of focusing on rare surnames is so that you can be more certain tha

It tracks rare surnames, so there aren’t many distant cousins to skew the results. The point of focusing on rare surnames is so that you can be more certain that people carrying them today are actually direct descendants of people in the old records. Second thing is that the fortune is typically not tracked here, because it’s really hard to get any historical data about fortune of any individuals, much less those not so famous. What Clark et al do is track status, and average out: for example, you can look at the people who graduated Oxford hundreds of years ago. As it turns out, their descendants today are overrepresented among UK’s doctors and lawyers. On the other hand, people carrying common job-related last names, like Smith or Taylor, are underrepresented as lawyers and doctors. In fact, in today’s UK, people carrying last names of Norman conquerors are still overrepresented among high status occupations in UK, although not by much, given a millennium of a regression towards the mean. I recommend reading the book, it’s great.