Monopolist’s Price Discrimination and Consumer’s Strategy: Group Buying

[[abstract]]傳統文獻在探討團購行為時，往往將之視為消費者的套利行為。當獨占廠商欲對消費者進行差別取價時，他必須考量消費者的各種套利行為，如借用入場證、代為採購及團購等行為，因為這些套利行為將削弱廠商的訂價能力。團購做為一種消費者的套利行為，乍看之下是一種對消費者有利，但對廠商不利的經濟行為，但在本文中，我們將試著提出一種相反的可能例子，在此例子中，廠商反過來利用消費者的團購行為，對消費者進行更嚴重的差別取價，以增加自身的利潤。本文中先介紹傳統模型，將消費者無團購行為的傳統模型做為廠商利潤比較的基準，接著將消費者團購行為納入模型後發現，如果廠商一昧的阻止消費者團購，將導致自身利潤的受損，此時廠商利潤將低於傳統模型。在第三個模型中，我們證明廠商可在維持傳統模型最適訂價下，藉由多增加團購商品組合使廠商的利潤增加（利潤高於傳統模型），另外，整體社會的效率也有所改進。最後則討論廠商增設團購商品組合的一般模型，在此模型下，我們可以發現沒團購能力的高需求消費者之福利降低，沒團購能力的低需求消費者之購買數量也降低。而有團購能力的低需求消費者則藉由此一新的交易方式提高其消費者剩餘，而廠商也藉此進一步地提高其獲利。[[abstract]]In the traditional literatures, economists who study group buying behavior usually regard it as consumer arbitrage. When a monopolist sets price discrimination to the consumers, he must consider their consumer arbitrage of different types, for example, borrowing cards from others, asking people to buy for them and group buying, because these consumer arbitrage behaviors will weaken the power for the monopolist to set price. Group buying, as one way of consumer arbitrage, at a glance, is advantageous to consumers; disadvantageous to the monopolist in economic activities, but in this article, we try to present a contrary example, in which, the monopolist attempted to make use of group buying behavior by setting more serious price discrimination to consumers in order to look for higher profit. In the beginning, the article introduces the traditional model, which is without group buying behavior, to be the monopolist’s profit comparison standard; then adding group buying behavior to this model, and we discovered that if the monopolist impeded group buying, they would have profit down, and the profit would be lower than that gained by the traditional model. In the third model, we proved that the monopolist could increase the profit (higher than that gained by the traditional model) if they maintained the traditional model’s optimal price setting with the combination of group buying bundle; besides, the efficiency of social welfare would be improved. Finally we discussed the model of the adding of group buying bundle, in which, we found the decrease in the welfare for both high-demand and low-demand consumers with no group buying capability. By this new transactional model, the low-demand consumers with group buy ability could have their consumer surplus raised; at the same time, the monopolist could further make better profit.[[note]]碩