RT Article T1 Third-Party Policing Approaches Against Organized Crime: An Evaluation of the Yakuza Exclusion Ordinances JF Journal of quantitative criminology VO 37 IS 3 SP 791 OP 811 A1 Hoshino, Tetsuya A2 Kamada, Takuma LA English YR 2021 UL https://krimdok.uni-tuebingen.de/Record/1767143028 AB Objective Third-party policing (TPP) refers to police efforts to persuade or coerce third parties to take some responsibility for crime control and prevention. The Yakuza Exclusion Ordinances (YEOs) of Japan aim to combat organized crime syndicates—the Yakuza. Consistent with the principles of TPP, the YEOs prohibit third parties (i.e., non-yakuza individuals) from providing any benefit to the yakuza. We argue that the effectiveness of the YEOs may depend on the strategic relationship among yakuza syndicates, where yakuza syndicates choose their power strategically to gain advantages over competition among rival yakuza syndicates. Methods We use unique data on the yakuza and construct a regional concentration index of yakuza syndicates. Exploiting prefecture-level variation in the YEOs’ enactment dates, we apply a difference-in-differences approach, while allowing for heterogeneity of the YEOs’ effect by the concentration of yakuza syndicates. Results The YEOs decrease the number of yakuza members and the effect of YEOs is greater in regions with lower concentration levels of yakuza syndicates. Given that yakuza members decrease by about 30% during the period of our study, our estimates suggest that the YEOs on average contribute to about 20% of a recent reduction of yakuza members. Conclusions The YEOs are related to TPP strategies that rely on coercive techniques, and thus our results suggest the effectiveness of TPP strategies against organized crime. Furthermore, the heterogeneity of the YEOs’ effect suggests the effectiveness of enforcement policies that intensively target regions with lower concentration of organized crime. K1 Quasi-experiment K1 Illegal markets K1 Organized Crime K1 Third-party policing DO 10.1007/s10940-020-09466-6