Being no government intervention, the upper procession obeys economic rule, urban periphery being shaped through looking for most efficiency, realizing rent balance and margin comparison.

• 排除政府干预，城市外围空间的扩展过程遵循经济规则，在谋求效用最大、实现地租均衡以及边际比较中形成城市的外围扩展空间。