The criterion of comprehensiveness refers to both a data set’s scope and richness of detail with respect to firearm-related violence.
Scope can be subdivided into the types of events that are captured and the populations covered. The scope of the NCVS, for example, is restricted to nonfatal incidents and to the characteristics of crime victims rather than offenders. Vital statistics and hospital-based information on firearm violence is also limited to the victims. The UCR, by contrast, captures information on both crime victims and offenders, but they are limited to offenses that are known to and recorded by law enforcement agencies. The NCVS includes data on both crimes reported to the police and those that victims do not report. Household-based surveys such as the NCVS and the GSS are limited to the population of persons with stable residences, thereby omitting transients and other persons at high risk for firearm violence. Such persons are included in the ADAM program, which collects information on persons who come into contact with the criminal justice system.
Geographic coverage is another dimension of scope. The GSS, for example, is representative of the United States and the nine census regions, but it is too sparse geographically to support conclusions at finer levels of geographical aggregation. This lack of individual-level data from small geographical areas is a significant shortcoming in the firearms data. Presumably, we would like to be able to make statements about, for example, the probability that an individual commits suicide conditional on owning a gun (or having one available) and other covariates. This cannot be done if the smallest geographical unit that the data resolve is a multistate region. Similar statements can be made about other forms of gun violence.
Perhaps no better illustration of the patchwork character of information on firearms violence in the United States exists than the multiple and nonoverlapping or partially overlapping coverage of the data sets. That should come as little surprise, inasmuch as many of the data sets were expressly intended to provide information about crime, violence, or injury that was not available from other sources. The major impetus for the development of the NCVS, for example, was to gather information on crime incidents that do not come to the attention of law enforcement agencies. The collection of information on violence from hospitals and emergency departments is intended to reveal types of violence, such as partner abuse, thought to be underreported in crime data sources.
The patchwork of existing data sources, in other words, has been created with the best of intentions and has shed light on aspects of violence, including the role of firearms, that otherwise would have remained hidden