Horizontal Mergers with Productive Efficiency Changes: An Asymmetric Firms Model

[[abstract]]考慮廠商合併後生產效率會變動，本文探討在不同利潤分配規則下，市場佔有率大小不等的廠商願意進行合併之條件，並且分析合併對社會福利的影響。由文中分析得知，若合併前廠商的市場佔有率越相近，則合併誘因越強；市場佔有率差異越大，則合併之誘因越薄弱。廠商合併誘因與合併後利潤如何分配有關，若合併後利潤之分配是依據合併前廠商的「利潤率」，則廠商合併的可能性大於依據合併前「市場佔有率」來分配的情況。不論利潤分配規則為何，只要市場規模夠大，即使合併後效率降低，廠商依然願意進行合併。對社會福利的影響可由產量的變化得知，合併前廠商的市場佔有率越近似，則合併對社會有益的可能性越大，但合併後的產量必須是合併前產量的82%之上，合併後社會福利才可能增加。合併前廠商的市場佔有率差異越大，則合併對社會有益的可能性越小，但合併後的產量若大於合併前產量，不論市場佔有率的差異性為何，合併必定可以增加社會福利。此外，本文對於公平交易委員會提出建言，期使公平交易法有關廠商合併之規範更適確。[[abstract]]In this paper, assuming that horizontal merger creates productive efficiency changes and firms are asymmetric before merger taking place, we explore the conditions that merger is beneficial for firms and examine the conditions that social welfare is increasing as horizontal merger happens. We demonstrate that if the market shares of firms are closer before merger occurs then it is more beneficial for firms. We also examine the impacts on the incentives for firms to merge by different profits-sharing rules after merger, which can be either Profit-ratio rule or Market-share rule. The taking place likelihood of beneficial mergers under Profit-sharing rule is larger than what under the Market-share rule. No matter what the profit-sharing rule is, we demonstrate that, while the market scale is large enough firms can be also beneficial from mergers even mergers with productive efficiency degenerate. We also find that, when mergers create productive efficiency synergies, the social welfare maybe increasing after mergers even the quantity produced is decreasing. Finally, we make some suggestions for the Fair Trade Commission to evaluate whether it should prohibit enterprises to merge