규제 샌드위치 효과: 플랫폼 규제 논의에 대한 기업 규모별 시장 반응

This study examines how policy discussions on expanding Korea's Broadcasting and Communications Development Fund to include online platforms affect platform firms' stock prices using event study methodology. We analyze the market reaction of 11 platform firms and 6 IT service firms to four major policy events from March 2024 to January 2025. Results show that platform firms experienced significantly larger negative returns than IT service firms during regulatory tightening events. Notably, we observe heterogeneous effects across firm sizes: while large and small platforms showed limited reactions, mid-sized platforms were most negatively affected. We term this phenomenon the “Regulatory Sandwich Effect,” suggesting that mid-sized firms face the greatest regulatory burden as they are subjected to regulations yet lack the adaptive capacity of large firms. Unlike large platforms, mid-sized firms have limited market power to absorb or pass on regulatory costs, restricted access to capital, and insufficient strategic flexibility to negotiate with regulators or exit the regulatory scope entirely. Analysis of variance confirms that tier-based differences were statistically significant at the 5-10% level across all regulatory tightening events, indicating that regulatory impact varies non-linearly with firm size. This study extends policy uncertainty theory and the resource-based view to the platform regulation context and highlights the importance of accounting for size-based heterogeneity in regulatory design.