[2Q5-GS-3] Knowledge utilization and sharing:

[2Q5-GS-3-04] Analysis of the Impact of Rate-Manipulating Users on CtoC Platforms

〇Ryoma Adachi¹, Yusuke Miyake², Fujio Toriumi¹ (1. The University of Tokyo, 2. GMO Pepabo, Inc.)

Keywords:Community Analysis, CtoC

In recent years, the CtoC market has rapidly expanded, leading to increased peer-to-peer transactions. However, fraudulent activities on these platforms have become a critical issue, particularly the manipulation of ratings through the misuse of the "favorite" function. This study analyzes data from the handmade CtoC platform "minne" to identify the behavioral characteristics of rate-manipulating users and their impact on the market. Users who meet specific behavioral criteria are defined as rate-manipulating users, and network analysis is employed to extract community structures. The results reveal that rate-manipulating users are concentrated within specific communities, with their influence being largely confined to these groups. Furthermore, a time-series analysis using Sankey diagrams demonstrates that rate-manipulating users tend to remain within the same community over time. This study aims to clarify the nature and characteristics of fraudulent behavior and provide guidelines for enhancing the integrity of CtoC platforms.