In 1991, the Nobel laureate economist Paul Krugman, who is perhaps the world’s leading Keynesian today, showed that whether or not expectations are self-fulfilling depends on underlying economic conditions. If an economy’s fundamentals are very weak, a crisis will inevitably occur sooner or later; if its fundamentals are very strong, a crisis never happens; and if they are in an intermediate range, a crisis happens if – and only if – people expect one.
1991年，诺贝尔经济学奖得主保罗·克鲁格曼（也许是当今世界最具威望的凯恩斯主义者）告诉人们预期能否自我实现取决于基本的经济条件。如果经济基本面非常薄弱，危机迟早会不可避免的发生；如果基本面非常强劲，危机永远不会发生；但如果基本面不上不下，那么危机有且只有在人们预期发生时才会发生。