First, this study briefly discusses arguments that it has a limitation to apply results from the extensive literature on the impact of competition on innovation incentives in a horizontal merger context and recent studies that examine more directly the effects of merger on innovation incentives.

Next, taking into account that the recent studies mostly focus on the effects of merger on intensive margin of innovation incentives, this study analyzes the effects of merger on extensive margin of innovation incentives and on R&D project choice. It is shown that (i) a horizontal merger induces merging firms to choose less differentiated R&D projects compared to a situation in which those firms choose their R&D projects independently without the merger if the probability of achieving a successful innovation is relatively high and more differentiated R&D projects in the opposite case; (ii) A horizontal merger can increase the number of R&D projects pursued by merging firms if the probability of achieving a successful innovation is relatively low and R&D cost is relatively high but decrease it if the probability of achieving a successful innovation is relatively high and R&D cost is relatively low. (iii) The impact of the horizontal merger on innovation competition is not clear, and consequently, consumer and social welfare may increase by the merger when the merger intensifies innovation competition.

Finally, this study examines relevant regulations and merger control cases to provide policy implications.

Preface
Executive Summary

Chapter 1 Introduction

Chapter 2 Discussion on Mergers and Innovation Competition
　Section 1 Economic Debates on the Relationship Between Competition and Innovation
　Section 2 Recent Discussions on the Impact of Mergers on Innovation Competition
　Section 3 Significance of This Study

Chapter 3 Impact of Mergers on R&D Decisions and Welfare
　Section 1 Analytical Model
　Section 2 Equilibrium Analysis Without Mergers
　Section 3 Equilibrium Analysis With Mergers
　Section 4 Comparison of Equilibrium Outcomes With and Without Mergers
　Section 5 Additional Discussion
　Section 6 Conclusion

Chapter 4 Merger Control Regulations and Cases on Innovation Competition: Policy Implications
　Section 1 Innovation Competition in Merger Review Guidelines
　Section 2 Innovation Competition in Merger Review Cases in the US and EU
　Section 3 Summary and Policy Considerations

Chapter 5 Conclusion
　Section 1 Key Research Findings
　Section 2 Limitations of This Study

References
Appendix
ABSTRACT