隨著多媒體技術的進步與多樣化，網路零售商提供完整資訊服務的費用也隨之變得越來越昂貴；但在電子商務環境中，大部份零售商所提供的資訊服務都具有公共財之特色，消費者可透過網路輕易地找到欲購買產品的免費資訊服務。然而，由於網路搜尋速度急遽地提升，使得網路購物的消費者能夠在低搜尋成本的情況下，迅速地在不同替代零售商間作購買抉擇，導致 消費者可能先向提供資訊服務的零售商尋求免費的服務支援，而最後卻再向無提供任何資訊服務但價格較低廉的零售商消費，造成搭便車問題的發生。當搭便車問題發生時，會降低零售商提供資訊服務的動機，以避免提供免費資訊服務的成本損失；但當大部分的網路零售商減少提供資訊服務內容時，卻可能造成整個市場的需求量大幅降低且自己本身亦陷入與其他競爭零售商相互價格競爭的困境中。

因此，本研究探討在搭便車問題存在的情境下，當消費者對欲購買的產品有不同資訊瞭解的程度時，網路零售商應如何制定競爭策略，方能從競爭市場上獲取最大利潤。本研究最後加以探討不同情境參數對網路零售商競爭策略以及整體社會福利之影響。

The E-retailers' costs of providing the complete information services increased because of the
progress and diversity of multimedia technology. However, in the E-commerce environment the
information services share the characteristics of a public good that E-customers could use the
Internet to easily find the ideal product that they desire to buy. Yet, the Web search speeds up
dramatically.Hence the E-customers can choose products among the similar E-retailers rapidly at
lower search cost. So the customers may consult the E-retailers who provide free information
services in advance,then take a "free ride" by purchasing from low-price sellers who do not
provide any information service. In a free riding environment, the E-retailers' incentives of
providing free information service will reduce in order to avoid presale cost. But when most
E-retailers lessen the incentives of providing free information services, it will also decrease
the demand for the product and cause a more intensive price competition.

Therefore, this thesis discusses the free rider problem when E-customers have different product
information knowledge, and how E-retailers formulate competitive strategies to earn maximum
profit in the market. It will also discuss the effects of different strategy parameters on
E-retailers' competitive strategies and social welfare.

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