양면시장에서는 기존의 전통적 산업조직이론이 적용되지 않거나 수정이 필요하다. 이는 양면시장의 가장 큰 특징 중에서 하나인 교차네트워크 외부성에 의한 것이다. 따라서 양면시장에서는 시장획정, 시장지배력 평가, 불공정행위 판단 등에 대한 기준이 단면시장에서의 그것과는 달라져야 한다. 경제이론에서는 시장이 주어진 하나의 조건이지만, 현실에서는 정의하여야 할 대상이다. 따라서 특정시장이 양면시장인지 아닌지의 여부를 명확히 판단하는 것은 중요한 과정이라 할 수 있다. 하지만 현재까지 특정시장이 양면시장인지의 여부를 판단하는 기준이 미흡한 것이 실정이다. 이는 관련 플랫폼에 대한 명확한 이해와 정의, 참여 소비자 그룹의 정확한 정의(identification) 등이 부족하기 때문이다. 이에 따라 본 본문에서는 양면시장의 정의와 특정시장이 양면시장인지의 여부를 판단하는 조건 등을 살펴보고자 한다.
The traditional theories in industrial organization economics such as inverse elasticity pricing rule, price discrimination may not applied or should be modified when we deal with two-sided markets. This comes from the special characteristic of two-sided markets especially cross network externality between two different groups of consumers (or suppliers).
For the same reason, the traditional market definition methods, market power evaluation, criteria for anti-competitive behaviors should be modified in two-sided markets. Thus if we use the traditional theories without modification when we consider issues of two-sided market, there is possibility to commit type I or type II errors. For example, the pricing under marginal cost of dominant firm is regarded as predatory pricing in one-sided market. But in two-sided market it is not anti-competitive predatory pricing but just profit maximization behavior.
Therefore it is very important to clarify whether the market is one-sided or two-sided(or multi-sided). However the structure of market is just treated as a given condition when we construct a theoretical model. But in the real world, market is not a given condition but an object to be defined. But until now there is no clear definition and criteria to decide whether the market is two-sided or not. The only academic definition is the Rochet & Tirole (2004)'s definition. And the most popular conditions of two-sided market is Evans (2003), and Evans & Schmalensee (2008)'s condition. But the condition is only necessary condition for two-sided market.
Thus this paper tries to introduce more clear definition and decision criteria of two-sided markets. We introduce axioms of no-side-payment, cross network externality etc to define two-sided market. And we introduce an algorithm to decide whether a market is two-sided or not.