商品多樣化規模效果、企業竊取效果與最適政府支出

Increasing Returns to Specialization, Business Stealing, and Optimal Government Spending

本文採用Bénassy（1996）提出的不完全競爭市場結構模型，首先，推導市場競爭與柏拉圖最適配置下的一般均衡解，並進一步透過模型校準分析方法探討最適的政府支出。我們的分析顯示，資本存量、消費量、產出及廠商家數在柏拉圖最適配置下可能高於或低於市場競爭均衡的水準，端視企業竊取效果（business stealing effect）和商品多樣化規模效果（increasing returns to specialization）相對大小而定。經由校準分析法的結果顯示，浪費性政府支出不再具有增進社會福利的效果。此結論打破了Devereux et al.（2000）的命題：認為在市場存在商品多樣化規模效果的情況下，柏拉圖最適配置下均衡解一定大於市場競爭均衡，且政府支出能促進社會福利的結論。

By using Bénassy’s (1996) model setting to separate increasing returns from imperfect competition, we show there are two opposite effects, the external effects of increasing returns to specialization and of business stealing, in terms of governing the relative levels of variety in a competitive steady state and optimal steady state. By shedding light on the business-stealing effect which is absent in the analysis by Devereux et al. (2000), we show that the steady-state levels of capital, consumption, and output in the social optimum can be lower, rather than higher, than those in a monopolistically competitive equilibrium. Further, we also find that the required extent of increasing returns to specialization for a positive level of optimal wasteful government spending seems to be too high to be empirically plausible. This implies that government spending is no longer welfare improving.