The price of a haircut in Dakar challenges a tenet of economics

seems oversupplied with theory—all dogmatic assumptions and curves with obscure names. Yet economics students in the rich world can get surprisingly practical advice from wild-haired professors explaining non-tradable goods: “When in poor countries, get a haircut.”The prices of goods that are traded internationally should not vary nearly as much as prices of things like haircuts that cannot be stored or shipped. This is because a trim depends largely on local costs such as wages, which are much lower in poor countries.