混合市場結構、市場集中與福利

Mixed Market Structures, Concentration and Welfare

本文建構了一個允許寡占大廠與完全競爭小廠並存競爭的環境，以探討內生廠商效率與大廠擴張的問題。廠商可以通過特有的研發投資取得不容忽視的市場力量，並經由出口、產品線擴張，以及收取更高的加價來擴大廠商營運規模。本文利用比較靜態分析探討貿易自由化對廠商行為和市場結果的影響。首先，貿易自由化使得廠商更容易進入海外市場，廠商為服務海外市場所增加的研發投入同時也擴展了國內市場的產品線與營收。除此之外，貿易將致使經濟資源和利潤重新配置到高效率大廠，因而助長了市場集中度和平均加成率，這樣的結果可望提高社會福利。

This paper explores endogenous firm efficiency with extensive margins within a framework where large oligopolists coexist with a monopolistically competitive fringe. The adoption of firm-specific R&D gives adopters non-negligible market power over nonadopters, which enables them to expand through exporting, extensive margins and charging higher markups. We study the comparative statics to examine the effects of trade on firm behaviors and market outcomes. The model predicts that trade liberalization increases the R&D of exporters serving foreign markets, which in turn increases domestic sales by widening domestic product lines. Trade-driven increases in market concentration and aggregate markups may be beneficial for the economy by reallocating economic resources and profit towards high-efficiency firms.