More Guns, More Crime
利用独特数据集估计美国各州和县级过去二十年的枪支拥有率，发现枪支拥有率上升显著增加枪支杀人案，但对其他犯罪影响较小；1993年以来枪支拥有率下降可解释枪支杀人相对非枪支杀人下降的三分之一。
This paper examines the relationship between gun ownership and crime. Previous research has suffered from a lack of reliable data on gun ownership. I exploit a unique data set to reliably estimate annual rates of gun ownership at both the state and the county levels during the past two decades. My findings demonstrate that changes in gun ownership are significantly positively related to changes in the hom-icide rate, with this relationship driven almost entirely by an impact of gun ownership on murders in which a gun is used. The effect of gun ownership on all other crime categories is much less marked. Recent reductions in the fraction of households owning a gun can explain one-third of the differential decline in gun homicides relative to nongun homicides since 1993. I.