Platform Power Under Asymmetric Market Evolution: Evidence from Korean Home Shopping

Platform markets are concentrating, even as their content suppliers fragment, yet this asymmetric evolution is poorly understood. Using panel data from 11–12 Korean home shopping firms (2015–2023), we employ Hansen threshold regression, instrumental variables, and panel fixed-effects models to examine its competitive impact. Our analysis of 104 firm-year observations reveals four key findings. First, platform concentration alone explains 94.4% of transmission fee variation, with fees rising from 41.15% to 68.72% as platform HHI increased from 1390 to 2154 while content HHI declined from 1797 to 1118. Second, we identify critical fee thresholds at 62.2% ( p = 0.012) and 73% ( p = 0.002) that divide markets into three distinct operating regimes. Third, the fee–profitability relationship reversed from negative (r = −0.145) to positive (r = 0.554), indicating fees’ evolution from cost burdens to selection mechanisms. Fourth, instrumental variable estimates (0.473) exceed OLS estimates (0.184) by 2.6 times, revealing severe selection bias. Simulations indicate a 60% fee cap would affect 25 firms (24%) while increasing total surplus by 15.1% and improving SME profitability by 2.9 percentage points. We propose the Asymmetry Ratio (Platform HHI/Content HHI) as a regulatory tool, with ratios exceeding 1.0 triggering enhanced scrutiny. Our findings demonstrate that asymmetric market evolution creates new sources of platform power requiring novel regulatory approaches.