Objectives: Focused deterrence seeks to change the violent behavior of gangs not directly targeted by the intervention by leveraging network ties between groups. This study appraises group-based and place-based methodologies in detecting direct and spillover crime reduction impacts of a focused deterrence strategy implemented in Oakland, California. Method: Quasi-experimental designs and panel regression models were used to compare shooting trends for directly treated gangs and census block groups to shooting trends for comparison gangs and block groups that did not directly receive the treatment. The design further analyzed whether vicariously treated gangs and untreated block groups immediately surrounding treated block groups experienced spillover shooting reductions. Results: The focused deterrence program generated statistically significant direct reductions in shootings in treated block group areas and by treated gangs relative to shootings in untreated block group areas and by untreated gangs, respectively. Spillover deterrent effects of varying magnitudes were found when shooting trends by vicariously treated gangs and in surrounding block groups were compared to shootings trends in comparison units. Conclusions: Group-based evaluation methodologies were better positioned to detect changes in violent gang behaviors after treatment and to shed light on deterrence mechanisms supporting program efficacy. Future focused deterrence studies should be theory driven rather than black box evaluations.

中文翻译：

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街头帮派，枪支暴力和集中威慑：比较基于场所和基于群体的评估方法以估计直接和溢出威慑效应

目标：集中威慑力求通过利用群体之间的网络联系来改变并非干预直接针对的帮派的暴力行为。这项研究评估了基于团体和基于地点的方法，以检测在加利福尼亚州奥克兰实施的重点威慑战略对减少直接和溢出犯罪的影响。方法：使用准实验设计和面板回归模型比较直接治疗的帮派和人口普查区组的射击趋势与未直接接受治疗的比较帮派和区组的射击趋势。该设计进一步分析了经过处理的团伙和紧邻处理的街区组的未经处理的街区组是否经历了溢出射击的减少。结果：集中威慑计划相对于未经处理的街区组区域和未经处理的团伙，分别在经过处理的街区组区域和经处理的团伙的枪击事件产生了统计上显着的直接减少。将经过精心处理的团伙和周围街区的射击趋势与比较单位中的射击趋势进行比较时，发现了不同程度的溢出抑制作用。结论：基于群体的评估方法更适合发现治疗后的暴力团伙行为变化，并阐明支持项目效力的威慑机制。未来的威慑研究应以理论为基础，而不是黑盒评估。