早期市場，因代理商獨占局面，消費者只能有單一的選擇。如今，隨著網際網路蓬勃發展及國際貿易活動往來日益頻繁，於是平行輸入商品亦加入了市場競爭，使得市場之競爭更為激烈，因此代理商的商品價格及售後服務策略應如何擬定將顯得格外重要。
近年來，隨著顧客之個人權利意識上漲，代理商需增設銷售服務據點及提供優質的售後服務，也需花費高額廣告金額，增加產品曝光度，以獲得顧客的青睞，而平行輸入貿易商則會以搭便車（free-riding）的方式，免費享有這些活動，因此平行輸入商品有低成本優勢，而代理商有原廠技術提供、完善服務據點及堅強維修服務團隊，具有售後服務上的優勢。因此本研究將鑒於上述之競爭模式，針對代理商提供原廠商品及原廠售後服務，平行輸入貿易商提供平行輸入商品及副廠售後服務，透過同時賽局競爭模型分析，探討代理商及貿易商之最適策略。研究結果發現代理商在商品方面，有效降低商品成本，會使得商品更有競爭力，商品利潤及市場佔有率也會增加；貿易商在售後服務方面，有效降低服務成本，會使得服務水準提高，售後服務利潤及市場佔有率也會增加。在差異程度方面，發現代理商拉大商品及售後服務之差異化，會對代理商帶來更大的利潤。

With the advent of the Internet and the popularity of international trade, consumers have more sources of products, such as from agents who are licensed by the original factories in addition to merchants without the license of the original factories, so that the interaction between agents and merchants becomes more important in practice. In the study, we investigate the strategies of price and service in a duopoly with an agent and a merchant, who sell products as well as provide after-sales service to consumers. We consider that the agent provides more information in the physical stores, and invest great advertising budget in promotion; whereas the merchant free rides these business activities without bearing fares, and capture a portion of the market with lower price. The agent, however, provides the better after-sales service than the merchant, because of the support from the original factory. We characterize the agent's and merchant's equilibrium decisions of prices and service in a simultaneous game, and derive the closed-form solutions to explore the effects of parameters on the members' profits and market-share rates. We find that both the agent and merchant will increase their service levels by lowering the service costs, and the merchant will also improve market share and benefit from the lower service cost. Moreover, the agent can benefit from the greater substitutabilities or after-sales service between the agent and the merchant.

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