Competition and Regulatory Policy for Multi-Sided Platforms with Applications to the Web Economy

This article is about a type of business that connects distinct groups of customers on a "multi-sided platform." Such businesses have been around for millennia. But their economic importance has increased with the Internet revolution. Many significant web-based businesses such as eBay, Facebook, and Google are multi-sided. Multi-sided platform businesses must account for the fact that each type of customers they attract values more of the other type of customers. Buyers value many sellers and sellers many buyers, for example, on Internet auction sites. That interdependence has significant implications for the economic behavior of these businesses (they often break even or lose money on customers on one side) and for how competition authorities and regulators should analyze them (market definition must account for the linkages between the multiple customer groups). Multi-sided platforms tend to engage in complex business practices. The challenge for policymakers is distinguishing anticompetitive from complicated but benign behavior. This paper is based on the Beesley Lecture, sponsored by the London Business School and the Institute for Economic Affairs, which I was invited to deliver on 26 October 2007 in London