NEGATIVE EXTERNALITIES, COMPETITION AND CONSUMER CHOICE*
研究了选择性负外部性如何影响竞争均衡和减少外部性的公共政策的合意性，发现价格效应可能使负外部性产品的销量随外部性增大而下降，从而竞争的正效应可能超过外部性的直接负效应，导致扩大外部性的政策反而可能提高福利。
Consumers sometimes make choices that impose greater external costs on those who do not make the same choice. This paper examines how the selectivity of negative externalities in such situations affects the competitive equilibrium and the desirability of an externality-reducing public policy. Selective negative externalities create network externalities, but outcomes may differ greatly from typical network effects. Price effects may cause the imposing product's sales to decline with the size of the negative externality. Consequently, a positive competitive effect may overwhelm the externality's negative direct effects on welfare, such that a policy that enlarges the externality may improve welfare.