Gun Prevalence, Homicide Rates and Causality: A GMM Approach to Endogeneity Bias
Gary Kleck, Tomislav Kovandzic, and Mark E. Schaffer.
Ideas at the Department of Economics, College of Liberal Arts and Sciences, The University of Connecticut
November, 2005
http://ideas.repec.org/p/cpr/ceprdp/5357.html

“This study seeks to answer the question of whether more guns cause more crime, and unlike nearly all previous such studies, we properly account for the endogeneity of gun ownership levels. ” The paper is available for download in multiple formats from this site.