IN AUGUST 1960 Wolfgang Stolper, an American economist working for Nigeria’s development ministry, embarked on a tour of the country’s poor northern region, a land of “dirt and dignity”, long ruled by ...

Wolfgang F. Stolper, 89, an economist whose work included a theory used to explain the effect of international trade on wages, died Monday in Ann Arbor, Mich., during surgery to clear a blood clot.

In a famous theorem, known as Stolper-Samuelson, he and a co-author showed that competition from imports of clothes and similar goods from underdeveloped countries, where producers rely on unskilled ...