Juju Wang points out that the "primacy theory" in national planning stresses that if there is a great disparity of development between the first and second cities of a nation, then it is not yet possible to consider it a developed nation.
王俊秀指出，都市研究裡的「首要理論」強調：一個國家的第一大都市和第二大都市如果差距過大，便不能稱之為已開發國家。