Third-Party Policing Approaches Against Organized Crime: An Evaluation of the Yakuza Exclusion Ordinances



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.


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.


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.


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.

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  1. 1.

    There used to be 22 designated yakuza syndicates, but in 2011, 2 of them, both of which operated only in Okinawa, merged.

  2. 2.

    In 2007, the Minister of Justice announced guidelines to reduce victimization (e.g., citizens, corporations, and governments) by the yakuza. The guidelines emphasize the importance of avoiding associating with the yakuza in any way, given that the association between the yakuza and non-yakuza may serve as income sources for the yakuza. Since this announcement was made, strategies for combating the yakuza have sought to emphasize severing the association.

  3. 3.

    There are some differences across prefectures. Under the YEOs, non-yakuza who make contracts are required to check whether the other parties to the contracts are related to yakuza. The relationship that has to be checked differs across prefectures. In a few prefectures, non-yakuza need to check only whether the other parties to contracts are yakuza members. Yet in Tokyo, non-yakuza need to check whether the other parties have been closely associated with the yakuza. This requirement in Tokyo is stringent, but in many other prefectures, non-yakuza are still required to ask the other parties to their contracts if at least five years have passed since they retired from their yakuza syndicates. This rule is often called a five-year rule.

  4. 4.

    This figure is based on the data by National Police Agency (2015). The reported number of yakuza members is the number reported in December of each year. For readers’ convenience, we report these numbers as the number of yakuza members in the subsequent years (e.g., the number in 2011 is the number as of December 2010). There are two types of yakuza members: regular members, who belong to particular yakuza syndicates; semi-regular members, who do not belong to but are allied with particular yakuza syndicates. Figure 1 plots the change in the total number.

  5. 5.

    The reason that the enactment dates are spread over about two years is that the YEOs are prefecture-level ordinances and the enactment dates vary from prefecture to prefecture.

  6. 6.

    To keep order, a yakuza syndicate may use violence against its members who violate its norms, even cutting off the offending members’ fingers. In the yakuza world, finger chopping can represent punishment or sincere apology and remorse. This tradition has been on the decline in recent years, but it remains in some areas. In recent years, yakuza members have increasingly been forced to pay money as a penalty. If they cannot pay, they may be punished violently.

  7. 7.

    In several prefectures, the YEOs were amended after their introduction. For example, Akita enacted YEOs in March 2011 and then amended them in July 2011. As we are interested in the TPP-like aspect of the YEOs, we define the enactment date as the date at which the clauses to regulate non-yakuza activity were incorporated. Accordingly, we define the Akita enactment date as July 2011. The YEOs were similarly amended in Tottori, Fukuoka, and Saga.

  8. 8.

    In “Appendix A”, we conduct several robustness checks using alternative indices. First, we use a time-dependent YCI. Second, we use alternative definitions of yakuza shares \(s_{pg}\) and a resulting YCI. Third, we use alternative indices for the regional competition among rival yakuza syndicates. Our empirical results are robust to all these specifications.

  9. 9.

    The represented estimates correspond to the estimates of \(\delta _{1}\) and \(\delta _{2}\) in the following regression:

    $$\begin{aligned} y_{pt}&= \delta _{1} YEO_{pt} \times Low_{p} + \delta _{2} YEO_{pt} \times High_{p} + \eta X_{pt} + \mu _{p} + \xi _{t} + \sum _{r \in R} \delta _{pr} \rho _{r} t + \varepsilon _{pt}, \end{aligned}$$

    where \(Low_{p}\) denotes the low YCI (less than or equal to the median) and \(High_{p}\) denotes the high YCI (greater than the median). This equation does not include the main term of the YEOs to avoid multicollinearity.

  10. 10.

    That is, we take the mean of the YCI variables and subtract this mean from each YCI variable.


  1. Abadie A, Diamond A, Hainmueller J (2010) Synthetic control methods for comparative case studies: estimating the effect of California’s tobacco control program. J Am Stat Assoc 105:493–505

    Article  Google Scholar 

  2. Abadie A, Diamond A, Hainmueller J (2015) Comparative politics and the synthetic control method. Am J Polit Sci 59:495–510

    Article  Google Scholar 

  3. Angrist JD, Pischke J-S (2008) Mostly harmless econometrics: an empiricist’s companion. Princeton University Press, Princeton

    Book  Google Scholar 

  4. Autor DH (2003) Outsourcing at will: the contribution of unjust dismissal doctrine to the growth of employment outsourcing. J Labor Econ 21:1–42

    Article  Google Scholar 

  5. Ayling J (2017) Combating organized crime Aussie-style: from law enforcement to prevention. In: Contemporary organized crime. pp 189–212, Springer, New York

  6. Bang H, Robins JM (2005) Doubly robust estimation in missing data and causal inference models. Biometrics 61:962–973

    Article  Google Scholar 

  7. Becker GS (1968) Crime and punishment: an economic approach. J Polit Econ 76:169–217

    Article  Google Scholar 

  8. Bertrand M, Duflo E, Mullainathan S (2004) How much should we trust differences-in-differences estimates? Quart J Econ 119:249–275

    Article  Google Scholar 

  9. Bjelland HF, Vestby A (2017) ‘It’s about using the full sanction catalogue’: on boundary negotiations in a multi-agency organised crime investigation. Pol Soc 27:655–670

    Google Scholar 

  10. Buerger Michael E (2014) Third-party policing. In: Encyclopedia of criminology and criminal justice. pp 5221–5232, Springer, New York

  11. Bulow JI, Geanakoplos JD, Klemperer PD (1985) Multimarket oligopoly: strategic substitutes and complements. J Polit Econ 93:488–511

    Article  Google Scholar 

  12. Clark RV (1997) Situational crime prevention. Successful case studies, 2nd edn. Harrow and Heston Publishers, Guilderland

    Google Scholar 

  13. Cornish DB, Clarke RV (2003) Opportunities, precipitators and criminal decisions: a reply to Wortley’s critique of situational crime prevention. Crime Prevent Stud 16:41–96

    Google Scholar 

  14. Dell M (2015) Trafficking networks and the Mexican Drug War. Am Econ Rev 105:1738–1779

    Article  Google Scholar 

  15. Dickenson M (2014) The impact of leadership removal on Mexican drug trafficking organizations. J Quant Criminol 30:651–676

    Article  Google Scholar 

  16. Goodman-Bacon Andrew (2018) Difference-in-differences with variation in treatment timing. Technical report, National Bureau of Economic Research

  17. Hainmueller J, Mummolo J, Yiqing X (2019) How much should we trust estimates from multiplicative interaction models? Simple tools to improve empirical practice. Polit Anal 27:163–192

    Article  Google Scholar 

  18. Hill P (2004) The changing face of the Yakuza. Global Crime 6:97–116

    Article  Google Scholar 

  19. Hill PBE (2003) The Japanese mafia: Yakuza, law, and the state. Oxford University Press, Oxford

    Book  Google Scholar 

  20. Kleemans ER, Huisman W (2015) Multi-agency approaches in ‘criminogenic’ settings: the case of the Amsterdam Red Light District. Crime Law Soc Change 64:247–261

    Article  Google Scholar 

  21. Levi M, Maguire M (2004) Reducing and preventing organised crime: an evidence-based critique. Crime Law Soc Change 41:397–469

    Article  Google Scholar 

  22. Mas-Colell A, Whinston MD, Green JR et al (1995) Microeconomic theory, vol 1. Oxford University Press, New York

    Google Scholar 

  23. Mazerolle L, Eggins E, Higginson A (2013) Third party policing for reducing crime and disorder: a systematic review. The Campbell Collaboration, Oslo

    Google Scholar 

  24. Mazerolle L, Ransley J (2004) Third party policing: prospects, challenges and implications for regulators. Regulation: enforcement and compliance, research and public policy series, pp 61–76

  25. Mazerolle L, Ransley J (2006) Third party policing. Cambridge University Press, Cambridge

    Book  Google Scholar 

  26. Milhaupt CJ, West MD (2000) The dark side of private ordering: an institutional and empirical analysis of organized crime. The University of Chicago Law Review, pp 41–98

  27. Montalvo JG, Reynal-Querol M (2005) Ethnic diversity and economic development. J Dev Econ 76:293–323

    Article  Google Scholar 

  28. Montgomery JM, Nyhan B, Torres M (2018) How conditioning on posttreatment variables can ruin your experiment and what to do about it. Am J Polit Sci 62:760–775

    Article  Google Scholar 

  29. National Police Agency (2009) Trends in the Yakuza (Boryokudan Josei)

  30. National Police Agency (2014) Trends in the Yakuza (Boryokudan Josei)

  31. National Police Agency (2015) White paper on police: special issue on the Yakuza (Keisatsu Hakusho)

  32. Nelen H, Siegel D (2017) Contemporary organized crime: developments, challenges and responses, vol 16. Springer, New York

    Book  Google Scholar 

  33. Peters M, Spapens A (2015) The administrative approach in the Netherlands. Administrative approaches to prevent and tackle crime: legal possibilities and practical application in EU Member States, pp 265–306

  34. Phillips BJ (2015) How does leadership decapitation affect violence? The case of drug trafficking organizations in Mexico. J Polit 77:324–336

    Article  Google Scholar 

  35. Ramseyer JM (2016) Nuclear power and the Mob: extortion in Japan. J Emp Legal Stud 13:487–515

    Article  Google Scholar 

  36. Rosenbaum PR (1984) The consequences of adjustment for a concomitant variable that has been affected by the treatment. J R Stat Soc Ser A (General) 147:656–666

    Article  Google Scholar 

  37. Rubin DB (1987) Multiple imputation for nonresponse in surveys. Wiley, Hoboken

    Book  Google Scholar 

  38. Webster J (2015) Effective third-party policing partnerships or missed opportunities? Pol Soc 25:97–114

    Google Scholar 

  39. Weisburd D, Majmundar MK (2018) Proactive policing: effects on crime and communities. National Academies Press, Washington

    Book  Google Scholar 

  40. Wing C, Simon K, Bello-Gomez RA (2018) Designing difference in difference studies: best practices for public health policy research. Ann Rev Publ Health 39

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We contributed equally to this study. We thank Daniel DellaPosta, Corina Graif, Takashi Harada, Noboru Hirosue, Hajime Katayama, Hanae Katayama, Yoshiki Kobayashi, Thomas A. Loughran, Yutaka Maeda, Mark Moore, Jun Nakabayashi, Kentaro Nakajima, Holly Nguyen, Wayne Osgood, Brian Phillips, Barry Ruback, Peter Reuter, Tomoyori Saito, Yoshimichi Sato, Stephanie M. Scott, Nobuo Suzuki, Christopher Winship, Letian Zhang, and the participants at the 38th Annual APPAM Fall Research Conference, Osaka University, Pennsylvania State University, and Tohoku University for their helpful comments and discussion. We also thank the editor and three anonymous referees for their comments. Kamada would like to thank Grant-in-Aid from the Japan Society for the Promotion of Science Fellows (26-5010). The usual disclaimer applies.

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Hoshino, T., Kamada, T. Third-Party Policing Approaches Against Organized Crime: An Evaluation of the Yakuza Exclusion Ordinances. J Quant Criminol (2020).

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  • Third-party policing
  • Organized crime
  • Illegal markets
  • Quasi-experiment