This study analyzes the differences between traditional cartels and platform cartels and examines their specific characteristics. First, unlike traditional cartels, platform cartels may take the form of partial cartels in which only some firms participate, excluding a dominant competitor. Second, such partial cartels may result in intensified competition with the dominant competitor. Third, as competition strengthens, there is a possibility of efficiency gains that improve the welfare of certain users. Therefore, the institutional framework for investigating and addressing platform cartels should be improved to take account of potential efficiency gains and the possibility of enhanced competition.

Chapter 2 derives these results using theoretical model analysis. When the model incorporates firm heterogeneity, partial cartels may arise even in traditional single-sided market settings. However, such partial cartels are formed not to compete against a dominant firm, but rather to eliminate competition among the participating firms themselves. In fact, once a partial cartel is formed, the number of effective competitors in the market decreases, which in turn weakens market competition.
By contrast, when two-sidedness and indirect network externalities are introduced, partial cartels can instead promote competition on the opposite side of the market and narrow the market share gap between the leading platform and the cartel-participating platforms. As a result, there is also a potential for efficiency gains that improve the welfare of users on the opposite side of the market. These outcomes arise because platforms that had previously lagged behind the leading platform in competition on the opposite side are now able to strengthen such competition by leveraging the cartel arrangement.

Chapter 3 examines existing competition law provisions relevant to the characteristics identified in Chapter 2. With respect to the potential for cartels to generate efficiency gains, the chapter reviews buyer cartels and countervailing cartels. Although the potential efficiency-enhancing effects of both have been extensively examined in academic and theoretical discussions, they have rarely received serious consideration in actual case enforcement. Because the nature and manifestation of efficiency gains from platform cartels differ from those in traditional contexts, institutional reform will be needed to ensure that efficiency effects receive more serious attention in enforcement.

Regarding conduct involving the exclusion of competing firms through joint coordination, the chapter examines the regulation of abuse of collective dominance and the regulation of concerted refusals to deal. Joint coordination that falls short of an explicit agreement has not been actively enforced in Korea to date. However, as demands may arise in the future to expand the scope of application of these regulations, it is necessary to study their potential applicability in advance.

Abstract (ENG)

Preface
Summary (KOR)

Chapter 1 Introduction
　Section 1 Background of the Study
　Section 2 Platform Cartels Aimed at Responding to Competition
　Section 3 Main Findings and Structure of the Report

Chapter 2 Theoretical Analysis: Incentives for Collusion Formation and Efficiency Effects
　Section 1 Basic Model: A One-Sided Market Model
　Section 2 Dominant Firm Model: A One-Sided Market Model
　Section 3 Platform Model
　Section 4 Efficiency-Enhancing Effects of Platform Collusion

Chapter 3 Institutional Analysis: Existing Competition Law Regulations and Implications
　Section 1 Regulation of Collusion and Efficiency Enhancement
　Section 2 Regulation of Joint Decision-Making Conduct and Anti-Competitive Effects
　Section 3 Concluding Remarks

Chapter 4 Conclusion and Policy Recommendations

References