By following rare surnames through elite rosters (universities, professions, legislatures) over centuries, Clark argues social mobility is much slower and more consistent across countries than standard parent‑child measures show. He also contends endogamy increases persistence and that racism and simple wealth inheritance cannot account for the patterns.
— This reframes equality‑of‑opportunity debates by suggesting deep, persistent family‑level advantages (e.g., inherited 'social competence' and assortative mating) drive outcomes more than near‑term policies alone.
The book’s method and findings: rare‑surname persistence across elite registers in England, the U.S., Sweden, India, China, Japan, Korea, Taiwan, and Chile, and the inference of a stable, slow mobility rate.