本文之主要目的在設立一寡佔模型，探討寡佔市場之均衡品質、服務量（產量）與社會最適品質、服務量（產量）之差異，並且討論市場結構對品質的影響。分析結果指出：市場均衡時之服務量較社會最適之服務量少，而市場均衡與社會最適品質之比較以及市場結構對品質的影響皆端頼「服務量對品質的邊際成本影響」符號而定。此一結果異於傳統文獻認爲「品質的變化受需求面因素影響」的結論。

This paper sets up a homogeneous oligopoly model to compare the equilibrium quality and service hours (or output levels) under profit maximization and social welfare maximization. It is shown that the total service hours is less under profit maximization than social welfare maximization. On the other hand, the quality difference under the two maximization methods are ambiguous as it depends on the effect of ser­vice hours to marginal cost, not depending on demand-side factors as prevailing in literature.