Natural curiosity and technological opportunities have driven me again:

Urban–Rural Shifts in Intentional Firearm Death: Different Causes, Same Results

Objectives. We analyzed urban–rural differences in intentional firearm death.

Methods. We analyzed 584629 deaths from 1989 to 1999 assigned to 3141 US counties, using negative binomial regressions and an 11-category urban–rural variable.

Results. The most urban counties had 1.03 (95% confidence interval [CI]=0.87, 1.20) times the adjusted firearm death rate of the most rural counties. The most rural counties experienced 1.54 (95% CI=1.29, 1.83) times the adjusted firearm suicide rate of the most urban. The most urban counties experienced 1.90 (95% CI=1.50, 2.40) times the adjusted firearm homicide rate of the most rural. Similar opposing trends were not found for nonfirearm suicide or homicide.

Conclusions. Firearm suicide in rural counties is as important a public health problem as firearm homicide in urban counties. Policymakers should become aware that intentional firearm deaths affect all types of communities in the United States.

Firearm suicide rates showed an increasing trend from urban to rural counties. The most rural counties experienced 2.09 times the firearm suicide rate of the most urban counties before adjustment. After adjustment, the most rural counties experienced 1.54 (95% CI=1.29, 1.83) times the firearm suicide rate of the most urban (P<.001). Conversely, firearm homicide rates showed a decreasing trend from urban to rural counties. The most urban counties experienced 3.04 times the firearm homicide rate of the most rural counties before adjustment. After adjustment, the most urban counties experienced 1.90 (95% CI=1.50, 2.40) times the firearm homicide rate of the most rural counties (P<.001; Figures 1 [triangle] and 2 [triangle]).


This case shows pretty well the law of small numbers as it is called by Kahnemann, and why we should be aware of it. This is the reason why cancer rater are both highest and lowest in small. poor rural areas voting Republican. Homicides happen thankfully very rarely even in the US, making it difficult to get big numbers for small counties. It would have very interesting to see the study without those two:

Code 10 Completely rural or less than 2500 urban population, adjacent to a metro area. 8.1 1.1
Code 11 Completely rural or less than 2500 urban population, not adjacent to a metro area. 17.0 1.5

Those 25% percent of the US counties contain just 2% of the population, bringing in the fearsome law of small numbers big time into the study. If you look closely this would mean however that we completely loss the only completely rural population codes.

A second paper, Deadly Violence in the Heartland: Comparing Homicide Patterns in Nonmetropolitan and Metropolitan Counties shows the very danger of this approach.

Similarly truncated variation may be found with other variables commonly associatedwith homicide, including poverty and percentage of the population that is African American (Kposowa & Breault, 1993). By including rural cases in the study of homicide, many problems resulting from truncated variation can be resolved. Significantly,the authors also found that of the 30 United States counties withthe highest homicide rates, 23 had populations of fewer than 20,000 people. Thus, although the most rural counties had lower homicide rates overall, there was substantial variation amongrural counties in the rate of homicide, a range of variation unmatched in purely metropolitan samples.
Later there is a nod to that problem...

A second impediment is methodological and reflects the added measurement difficulties of including rural areas in analyses because of their small populations and relatively small number of rare but important events, such as homicide. The results of this study affirm that including such areas is analytically, as well as empirically, important.
Time has run out. So I just will throw a couple of questions into the virtual room about crime (and guns). Tend certain crimes to be more of an urban problem because it is there 'where the money is'? Do rural and semi-rural areas lack a critical mass of say young men and good criminal business opportunities? Does a demographic adjustment with age groups in mind change relationships between more or less urban counties?