We explore the regulation of new software platforms that connect consumers with informal service providers for transportation, short-term rentals, and more. These platforms tend to be in tension with existing regulatory frameworks which typically require licensing, certification, and insurance. In one view, some of these requirements are outdated or protectionist, benefiting incumbents more than consumers. Others counter that the rules embody important values and protect both customers and the public at large. We explore these disagreements with an eye for how the regulatory framework might allow the key efficiencies these platforms provide, while assuring protection for customers and avoiding harm to noncustomers.

†We review the burgeoning literature on two-sided markets focusing on the different definitions that have been proposed. In particular, we show that the well-known definition given by Evans is a particular case of the more general definition proposed by Rochet and Tirole. We then identify the crucial elements that make a market two-sided and, drawing from both theory and practice, derive suggestions for the identification of the two-sided nature of a market. Our suggestions are relevant not only for the analysis of traditional two-sided markets, such as newspapers and payment cards, but also for the analysis of many new markets, such as those for online social networks, online search engines and Internet news aggregators. JEL codes: L40, L50, K21

Drawing from the economics of two-sided markets, we provide suggestions for the definition of the relevant market in cases involving two-sided platforms, such as media outlets, online intermediaries, payment cards companies and auction houses. We also discuss when a one-sided approach may be harmless and when instead it can potentially lead to a wrong decision. We then show that the current practice of market definition in two-sided markets is only in part consistent with the above suggestions. Divergence between our suggestions and practice is due to the failure to fully incorporate the lessons from the economic theory of two-sided markets, to the desire to be consistent with previous practice and to the higher data requirements and the higher complexity of empirical analysis in cases involving two-sided platforms. In particular, competition authorities have failed to recognize the crucial difference between two-sided transaction and non-transaction markets and have been misled by the traditional argument that where there is no price, there is no market.