本文考量外部效果受影響者從事的減輕（轉化）活動與各行為人的臆測變量，分析Pareto最適境界的條件與最適價格設計。考慮下列三項政策工具的效果：（1）對減輕活動課稅或補貼， （2）對減輕活動的淨產出課稅或補貼，（3）對外部效果承受人最終承受的外部性數量予以課稅或補貼；從其中選出能促使市場均衡達成Pareto最適境界的價格政策。本文的結論是，由於減輕（轉化）活動本身有外部效益，市場均衡通常不等於Pareto最適；因此，為了達成Pareto最適境界，政府是否須對受影響者課稅或補貼，視稅基為何，以及臆測變量的符號與大小而定。本文認為對受影響者課稅或補貼的關鍵因素不在於外部性本身的特性，而是在於轉嫁活動本身的特性而定。

The purpose of this paper is to study the optimal pricing policy for an economy with negative externalities and externality-mitigation (or transformation) activities, given that: 1) an externality-mitigation activity has nondepletable external benefits, and 2) people acting to mitigate (or transform) the negative externalities they bore consider the reactive action from their neighbors, and everybody involved in the game conjectures each other's action. The study investigates three potential pricing schemes corresponding to the Pareto optimum: 1) a tax or a subsidy on the mitigating activity, 2) a tax or a subsidy on the net output of the mitigating activity, and 3) a tax or a subsidy on the final bearer of the externality. The conclusion is that the choice of an optimal policy instrument - be it a tax or a subsidy on the mitigating activity, the net output of the mitigating activity, or the externality victims - depends on the direction and magnitude of the conjectural variations and the selection of the tax base. It is shown that whether a tax is required on or a subsidy is paid to the parties affected by a negative externality doesn’t depend on whether the externality is depletable or not, or whether it’s shiftable or not. Rather it depends on whether the shifting behavior has external costs or benefits.