本文於中間財市場為獨占性競爭的架構下, 考慮生產面存在聚集經濟效益, 中間商品多樣化對最終產出具規模報酬特性, 而家計單位的消費, 存在負的消費外部性的情況, 討論聚集經濟效益和消費外部性與經濟成長率的關係、 租稅政策之成長效果和最適租稅的制定。 本文的重要結論為: 聚集經濟效益愈大, 愈有利於經濟成長; 消費外部性與經濟成長率有正相關。 消費稅與所得稅的提高, 不利於經濟成長, 但對中間廠商的營運成本補貼, 有利於成長。 最適消費稅與消費及生產外部性的程度呈正相關, 但面對不完全競爭的商品市場, 應對要素所得補貼, 以矯正生產的無效率。 此外, 聚集經濟效益愈大, 對中間廠商的最適補貼率也愈高。

This paper analyzes the effect of agglomeration and a consumption exter-
nality, in the form of “keeping up with the Joneses”, on growth under the
framework of imperfectly competitive product markets. Consumption and
production externalities and imperfect competition not only break the link
between Pareto optimal and competitive equilibria, but also raise the issue of first-best fiscal policies. By considering the endogenously determined num-ber of intermediate firms, we show that agglomeration reinforces economic growth and a consumption externality leads to an inappropriately high eco-nomic growth rate under competitive equilibrium. Furthermore, consump-tion and income taxes lower growth, but a subsidy to intermediate firms’operation costs benefits growth. Finally, we show that the optimal con-sumption tax is positively related to the size of the consumption externality.
An optimal subsidy to offset the fixed cost and the degree of agglomeration
is also described. The optimal income tax is to pay a subsidy to labor and
capital in order to correct for production inefficiency.