Why do elite families remain at the top generation after generation?
Kumanomido, Takayasu: "Elite Persistence in Family: The Role of Adoption in Prewar Japan" CRC Discussion Paper No. 537
Why do elite families remain at the top generation after generation? New research using a historical dataset from prewar Japan uncovers a striking answer: adoption. Hiroshi Kumanomido (LMU Munich, Project B04) and Yutaro Takayasu (University of Tokyo) constructed a unique dataset of roughly 25,000 father-heir pairs from the Japanese Personnel Inquiry Records (PIR), which lists individuals among the top 0.1% of the population regarding social status between 1903 and 1939.
A key challenge in studying adoption is selection bias: families with weaker prospects for persistence may be more likely to adopt, masking adoption’s true benefits. To establish a causal link, the study leverages the inheritance law of prewar Japan, which only permitted the adoption of a son if the family lacked a biological male heir. This institutional rule allowed the use of the gender of the firstborn child as an instrument for the adoption decision, an approach validated by the finding that having a female firstborn increased the probability of adoption by 15.5 percentage points.
Using this instrumental variable approach, the core result shows that having an adopted heir increases the probability of maintaining elite status in the son’s generation by 27% compared to reliance on a biological heir. This adoption premium is primarily driven by an increase in heirs listed in the top 0.1% income distribution. The analysis further reveals that fathers who achieved great success early in life, or those who were expected to become elites from a young age (e.g., Imperial University graduates or samurai), had better access to high-quality adopted sons. Furthermore, the system appeared to mitigate intergenerational skill mismatch by recruiting heirs whose career trajectories matched those of their fathers.
Countering the view that adoption merely constructed closed elite networks, the findings indicate significant upward mobility at the individual level: approximately 57% of adopted heirs who achieved elite status came from non-elite biological families. This supports the argument that, for elite families in prewar Japan, adopting an heir successfully expanded the talent pool, demonstrating a powerful mechanism for elite continuity.
Link (pdf): Elite Persistence in Family: The Role of Adoption in Prewar Japan
