平台市場的三贏局面：Amazon、第三方賣家之間的競合關係與策略分析

Abstract

本研究旨在探討電子商務平台市場中，平台營運者（以Amazon為例）與第三方賣家之間的競合（Coopetition）關係，並嘗試找出在此互動關係下實現平台方、第三方賣家與消費者三贏局面的可能性。

過去相關文獻多著重於平台與賣家間的競爭或合作，較少考量消費者的相對福利變化，且部分模型設定未能充分反映實務情境。為填補此研究缺口，本文採用賽局理論作為分析工具，建立一套包含平台營運方與第三方賣家動態互動的數學模型，並改以斯塔克爾貝格模型為基礎，探討平台進入後雙方的策略行為及相對利益變化。同時，本研究亦將消費者福利納入分析架構，檢視不同市場情境（標準化產品市場與差異化產品市場）下，三方利益之互動關係與均衡結果。透過數值模擬與敏感度分析，研究結果顯示：在適當條件下，Amazon選擇進入市場銷售自營商品，並未必損害第三方賣家利益，反而可能透過外溢效果提升第三方賣家銷售表現，並改善消費者福利，實現三贏局面。此外，產品差異化程度、平台佣金比例、市場競爭程度和平台外溢效果等關鍵參數，均對競合關係及三方利益及市場局面產生顯著影響。

本研究有助於補足既有文獻的不足，並提供平台經營者在制定營運策略與政策時的參考，期望能促進平台生態系統中各方的良性互動與永續發展。

This study aims to explore the coopetition relationship between platform operators (using Amazon as an example) and third-party sellers in the e-commerce market, and to investigate the possibility of achieving a triple-win scenario among platform operators, third-party sellers, and consumers under such interactions.

Previous literature has primarily focused on the competition or cooperation between platforms and sellers, with limited attention paid to changes in consumer welfare. Moreover, some existing models fail to adequately reflect real-world market conditions. To address this research gap, this study adopts game theory as the analytical tool and constructs a dynamic interaction model between platform operators and third-party sellers, based on the Stackelberg model. The analysis examines the strategic behaviors and relative benefits of both parties after the platform's entry into the market. In addition, consumer welfare is incorporated into the analytical framework to assess the interactions and equilibrium outcomes of the three parties' interests under different market scenarios, including standardized and differentiated product markets. Through numerical simulations and sensitivity analyses, the results indicate that, under appropriate conditions, Amazon's decision to enter the market and sell self-operated products does not necessarily harm the interests of third-party sellers. On the contrary, it may enhance third-party sellers' sales performance through spillover effects and improve consumer welfare, thereby achieving a triple-win outcome. Furthermore, key parameters such as the degree of product differentiation, platform commission rates, market competition intensity, and platform spillover effects significantly affect the coopetition relationship, the interests of the three parties, and the overall market landscape.

This study contributes to supplementing the existing literature and provides a reference for platform operators in formulating operational strategies and policies, with the aim of fostering positive interactions and sustainable development among stakeholders within the platform ecosystem.