Multi-sided platforms (Hagiu and Julian, 2011) have gotten a lot of attention recently. Multi-sided platform sponsors aspire to open innovation. They link a relationship between multiple groups and construct a mechanism of co-creation. This paper is intended as an investigation of a process to create and develop multi-sided platforms. Specifically, we are concerned with an attractive factor to users in launching stage of platforms and a mechanism of getting an ongoing commitment in developing stage of platforms. The concept of “network externality” is helpful in understanding multi-sided platforms. Network externality is the effect that one user of a good or service has on the value of that product to other people. It works between sides of multi-sided platforms. When network externality is present, the value of a product or service is dependent on the number of others using it. Therefore, a platform become increasingly popular, as numbers of users is becoming above threshold level. It is important to identify an attractive factor to users in launching stage of platforms. Multi-sided platforms form a bridge between multiple sides (markets) and balance the conflicting interests. It can be presumed that interactions among a platform sponsor and multiple sides depend on whether each side is a business (B) or a consumer (C). We have proposed a model of creation and development of multi-sided platforms. As a platform is created, a platform sponsor orchestrates to attract demand side users and supply side users. It fosters trust and provides incentives to demand side users and supply side users. And it seeks to every side users’ retention in developing stage of its platform. As numbers of every side users are becoming above threshold level, network externality works and a platform become increasingly popular. As describe above, it can be presumed that interactions among a platform sponsor and multiple sides depend on whether each side is a business (B) or a consumer (C). Therefore, in this study, multi-side platforms are classified into three categories according to the combination of businesses (B) and consumers (C). As far as BtoB type platforms concerned, every side consists of businesses. In BtoC type platforms, consumers also behave as demand side users. For instance, they create word of mouth in a platform. ICT based Japanese multi-sided platforms were selected as a research site. This study is based on a comparative analysis between three types of multi-sided platforms. Data were collected from multiple sources and multiple viewpoints. Company documents were studied, interviews with key executives and managers undertaken. Through we do a comparative analysis between three types of multi-sided platforms, this study clarified the following three points: 1. BtoC type multi-sided platforms provide “information” as an attractive factor regarding an entry to the platform to demand side users. In contrast, this is not true of BtoB type platforms. “Information” is not an attractive factor to demand side users in launching stage of BtoB type platform. “Information” contributes to demand side user retention in developing stage of BtoB type platform. 2. BtoC type of multi-sided platforms have the higher cost of platform maintenance than BtoB type in that BtoC type manage “information” put out by consumers that is more diversity and emotional than businesses. 3. Platform sponsors do not seek their own gain and they aspire to the total optimization of their ecosystem and industry segments. “Neutrality” is common attitude to all type of multi-side platforms. BtoC type sponsors particularly focus on having a strong commitment to users view and pulling in more customers, not slaving to traditional business practices.

• Kotaro Sakata(Kobe University)