will give a presentation on:
Platforms often use fee discrimination within their marketplace (e.g., Amazon, eBay, and Airbnb specify a variety of merchant fees). To better understand the impact of marketplace fee discrimination, we develop a model that allows us to determine platform equilibrium fee, category, and retail entry decisions that depend on the extent of fee discrimination available to the platform. Isolating the effects of fee discrimination (by not allowing the platform to enter into commerce), we find that greater fee discrimination allows the platform to serve more markets in its marketplace but also worsens double marginalization in the high surplus markets. However, if the platform enters into retail, then the platform reduces its fees and generates greater retail competition. These effects mitigate distortions from fee discrimination and improve welfare. In terms of policy, we show that (1) banning fee discrimination and platform entry is detrimental to welfare, (2) a vertical merger within a retail market mitigates double marginalization but is often worse than an equilibrium with platform entry into retail, and (3) taxing the platform in retail (not merchants) levels the retail playing field and can generate a Pareto improvement upon a policy that bans platform retail entry.
Paper available here.