AMERICA and Japan top the charts for the highest rates of adoption—but with one big difference. Whereas the vast majority of adoptees in America are youngsters, in Japan children represent a tiny 2% of all adoptions. Men in their 20s and 30s make up the remaining 98%, or almost 90,000 adoptees in 2008 (up from fewer than 80,000 in 2000). Why are so many adults adopted in Japan? The reason is more mercantile than magnanimous. Business acumen and skill are not reliably hereditary. As a result, most family businesses wilt after their founder’s death. Just 37 members make up Les Hénokiens, a fraternity of companies worldwide that are at least 200 years old and are still run by a family member. The two firms which vie for the title of the world’s oldest family company are Hoshi, an inn founded in 781, and Kongo Gumi, a Buddhist temple builder from 578—and both are Japanese.

Before the second world war, Japan’s civil code decreed that family wealth passed along male lines; tradition dictated it went to the eldest son. In daughter-only households, this fuelled a demand for adopted sons who could carry on the family name and business. (If a biological son was deemed an unsuitable heir, he too could be bypassed for an adopted one.) In turn, families with a surplus of younger sons sent them out for adoption. Many legal adoptions are coupled with a form of arranged marriage (known as omiai) to one of the family’s daughters—but the son-in-law (or mukoyoshi) then changes his name to hers. Today a host of matchmaking companies and marriage consultants recruit voluntary adoptees for Japanese companies.

Although Japan’s post-war code no longer upholds primogeniture, business families find the habit hard to kick. The country's declining birth rate has further limited the likelihood of a male heir for many of them; bosses often select sons from among their most promising top managers. The family owners of Toyota and Suzuki, both carmakers, Canon, an electronics firm, and Kajima, a construction company, have all adopted sons to manage them. Incentives are high for prospective adoptees, too. Their birth parents sometimes receive gifts of many million yen. To be selected as a mukoyoshi is to be awarded a high executive honour. This prompts fierce competition among managers, ensuring that the business has access to as good a talent pool as non-family companies. In fact, researchers have found that adopted heirs’ firms outperform blood heirs’ firms—although the prospect of being overlooked for an outsider can serve as motivation for sons to knuckle down, too.

Update: This blog post has been amended to remove the news peg.

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