Knife-Edge or Plateau: When Do Market Models Tip?
研究双边互动模型中，代理人是否必须聚集于单一地点。模型存在促进聚集的递增收益效应，但拥挤或市场影响效应使代理人偏好同类较少的市场。研究发现模型不会像通常所说的那样倾斜，而是存在两个活跃市场的广阔高原，仅当某市场低于临界规模时才会倾斜。
This paper studies whether agents must agglomerate at a single location in a class of models of two-sided interaction. In these models there is an increasing returns effect that favors agglomeration, but also a crowding or market-impact effect that makes agents prefer to be in a market with fewer agents of their own type. We show that such models do not tip in the way the term is commonly used. Instead, they have a broad plateau of equilibria with two active markets, and tipping occurs only when one market is below a critical size threshold. Our assumptions are fairly weak, and are satisfied in Krugman's model of labor market pooling, a heterogeneous-agent version of Pagano's asset market model, and Ellison, Fudenberg, and Möbius' model of competing auctions.