In 2008, we explored the issue of whether more gun ownership meant more or less gun violence. What we found, and it still holds true, was that some studies had shown a statistical relationship between those factors ? areas with a higher prevalence of guns had higher prevalence of gun homicides and homicides in general. But studies haven?t been able to show a causal relationship ? that the mere presence of guns, as opposed to other factors, caused the higher rates of gun violence. It?s doubtful, however, that a study could ever beyond-a-doubt prove a causal relationship.
As Sorenson explained, scientists can?t conduct a random experiment. So, instead, researchers are left with statistical models, which are ?very fragile,? says Charles F. Wellford, who was chair of the committees that authored a lengthy 2004 report on this topic by the National Research Council of the National Academies. These models are subject to what control variables researchers use. ?Everyone knows there?s other things than guns that cause crime,? says Wellford, a professor in the Department of Criminology and Criminal Justice at the University of Maryland. So these models become very complex and slight changes can cause very different results, he says.
The National Research Council review of the available research on guns and crime found that studies comparing similar geographic areas, such as urban areas to urban areas, known as ?case-control studies,? showed that ?violence is positively associated with firearms ownership.? But when looking at larger areas, such as countries, the National Research Council report found ?contradictory evidence.? Both types of studies, said the report, failed to address factors involved in buying a gun ? it?s not a random decision. And gun ownership data itself is lacking ? it comes only from public opinion surveys.
Eighteen experts participated in the NRC report, including those in criminology, sociology, psychology, economics, public health and statistics. The NRC?s conclusion: ?In summary, the committee concludes that existing research studies and data include a wealth of descriptive information on homicide, suicide, and firearms, but, because of the limitations of existing data and methods, do not credibly demonstrate a causal relationship between the ownership of firearms and the causes or prevention of criminal violence or suicide.?
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