Online platforms provide sellers’ products on their websites and earn a commission fee for each unit sold. Recently, many platforms have tried to refer customers to their direct competitors. In this paper, we explain this counter-intuitive practice by developing a game-theoretic model where two competing platforms contracting with one common seller or two competing sellers. We first analyze a benchmark case where platforms and sellers are integrated, finding that competitor referral will aggregate competition and thus neither platform is willing to refer its competitor voluntarily. However, when each platform serves as a marketplace for an independent seller, it is possible that a platform voluntarily refers its competitor. The rationale is that there exists a double marginalization problem when platforms set commission fees and sellers set prices, resulting in low efficiency of product selling. By referring visitors to their competitors, platforms can introduce cannibalization to cope with the double marginalization problem. We also investigate the case when the two platforms serve one common seller, finding that as long as the seller does not charge discriminated prices for the same product, the platforms may also apply referral. This is because the benefits of the two platforms are more aligned when the common seller sets a common price. Thus, online referral which helps the competitor may also help the referring platform itself. This paper also makes serval extensions to check the robustness of the model.

在线平台在其网站上提供卖方的产品，并为每个出售的单位赚取佣金。最近，许多平台都试图将客户推荐给他们的直接竞争对手。在本文中，我们通过开发一种博弈论模型来解释这种违反直觉的做法，其中两个竞争平台与一个共同卖方或两个竞争卖方签订合同。我们首先分析一个基准案例，该案例将平台和卖方整合在一起，发现竞争对手的推荐会加剧竞争，因此没有一个平台愿意自愿推荐其竞争对手。但是，当每个平台都充当独立卖方的市场时，平台可能会自愿推荐其竞争对手。理由是平台设定佣金而卖方设定价格时，存在双重边缘化问题，导致产品销售效率低下。通过将访问者介绍给竞争对手，平台可以引入食人化来应对双重边缘化问题。我们还调查了两个平台为一个共同卖方服务的情况，发现只要卖方不对同一产品收取歧视性价格，该平台也可以申请推荐。这是因为，当共同卖方设定共同价格时，两个平台的收益会更加一致。因此，可以帮助竞争者的在线推荐也可以帮助推荐平台本身。本文还进行了服务扩展，以检查模型的鲁棒性。我们还调查了两个平台为一个共同卖方服务的情况，发现只要卖方不对同一产品收取歧视性价格，该平台也可以申请推荐。这是因为，当共同卖方设定共同价格时，两个平台的收益会更加一致。因此，可以帮助竞争者的在线推荐也可以帮助推荐平台本身。本文还进行了服务扩展，以检查模型的鲁棒性。我们还调查了两个平台为一个共同卖方服务的情况，发现只要卖方不对同一产品收取歧视性价格，该平台也可以申请推荐。这是因为，当共同卖方设定共同价格时，两个平台的收益会更加一致。因此，可以帮助竞争者的在线推荐也可以帮助推荐平台本身。本文还进行了服务扩展，以检查模型的鲁棒性。可以帮助竞争者的在线推荐也可以帮助推荐平台本身。本文还进行了服务扩展，以检查模型的鲁棒性。可以帮助竞争者的在线推荐也可以帮助推荐平台本身。本文还进行了服务扩展，以检查模型的鲁棒性。