富人越来越多的把收入份额花费在服务上，这些服务要么是不可能进行贸易（例如，外出用餐 ） ， 要么是难以贸易（如卫生服务 ） 。
Richer people spend an increasing share of their income on services that are either impossible to trade (for example, restaurant meals) or difficult to trade (such as health services).