2025 Volume 9 Issue 2 Pages 63-86
Digital display advertising, which accounts for approximately half of Japan's internet advertising revenue, fundamentally depends on user identification and tracking. Traditional tracking methods using third-party cookies and mobile advertising identifiers have faced mounting challenges amid escalating societal demands for privacy protection. Compounding these difficulties, the progressive digitization of both consumer behavior and physical retail has led to severe data fragmentation. Marketing data is scattered across disparate systems, each employing different identifiers, controlled by different entities, and collected in varied contexts. This fragmentation presents substantial operational challenges for marketers and advertisers alike. Data Clean Rooms (DCRs) have emerged as a promising technological solution, enabling collaborative analysis of fragmented datasets without requiring data owners to directly disclose their underlying information. This paper proposes a functional taxonomy for DCRs in the targeted advertising context, identifying four core capabilities: (1) Data Enrichment, (2) Statistics and Model Creation, (3) Activation, and (4) Advertising Effectiveness Measurement. Through systematic analysis, we identified 23 distinct data flow patterns across these four functional categories. We subsequently examined the obligations imposed by the Act of the Protection of Personal Information (APPI) on advertisers, partners, and DCR vendors for each of these 23 patterns. Our analysis reveals a critical finding: even when DCRs provide technical guarantees preventing direct data disclosure, no patterns exist where APPI obligations are circumvented or exempted. Finally, through examining the data transfers necessary to deliver all four DCR functions, we establish that all DCR participants should properly characterize data provision associated with DCR usage as constituting third-party provision of personal data under APPI. These findings have significant implications for DCR implementation and compliance strategies in Japan's digital advertising ecosystem.
