Interpreting some charts about guns

Felix linked to a set of charts about guns in the U.S. (and elsewhere). The original charts, by Liz Fosslien, are found here.

I like the clean style used by Fosslien. Some of the charts are thought-provoking. Many of them may raise more questions than they answer. Here are a few that caught my eye.

A simplistic interpretation would claim that banning handguns is futile, and may even have an adverse impact on murder rate. However, this chart does not reveal the direction of causality. Did some countries ban handguns because they are reacting to higher violence? If that is the case, this chart is confirming that the countries with handgun bans are a self-selected group.

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The U.S. is an outlier, both in terms of firearm ownership and firearm homicides. This makes the analysis much harder because the U.S. is really in a class of its own. It's not at all clear whether there is a positive correlation in the cluster below, and even if there is, whether we can draw a straight line up to the U.S. dot is also dubious.

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Fosslien is being cheeky to deny us the identity of the other outlier, the country with few firearms but even higher death rate from intentional homicide. These scatter plots are great by the way to show bivariate distributions.

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I'd still prefer a line chart for this type of data but this particular paired bar chart works for me as well. The contents of this chart is a shock to me.

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I just don't get this one. Why is there a fan?

Comments

[Sib313]

The first chart looks like the countries are deliberately selected to obscure the comparison rather than to reveal anything. The snapshot of single time point comparisons leaves many questions about the comparability unanswered.

A better analysis would be to compare the rates over time within each country before and after a ban (and maybe for a larger group that actually included some of the key countries like Australia or the UK who used to allow some guns and now don't). This before and after comparison removes a lot of the inherent differences among countries and directly addresses the question.

The current country selection is clearly biased by the omission of the UK anyway since we are one of the larger examples of a country where handguns were allowed but are no longer allowed.

[Rhonda Drake]

Kaiser for the second chart where the US is identified in the gold point there is another outlier on the dimension of intentional homicides per 100,000 people. What country is that? Do we know? It might help put the data relationship in context.

[Ken]

The sources are given at the end of Fosslien's page. The homicide rates are from http://www.unodc.org/unodc/en/data-and-analysis/homicide.html The problem is that the plot only uses a selection of these. Many third world countries have much higher homicide rates than the US. The omissions are probably because they don't have data on gun ownership.

[Kevin Henry]

In the first chart, it's not clear how the countries are ordered within each group. Certainly, the effect of putting Russia last in the 'Handguns banned' area, right next to the very-low Poland data point, has the effect of heightening the contrast between the two groups.

Imagine if the chart was ordered from most murders to least (so: Russia, Belarus, Luxembourg, Finland, Poland, Belgium, France, Germany, Norway). Sure, the 'Handguns banned' group would still be noticeably higher, but I think the smooth shape would lessen the subjective impact of the difference.

When arbitrary, unconstrained changes to the layout can cause such noticeable differences in the impression, it's a good sign that you might have the wrong chart design.

[Gun Guru]

State-by-state figures are also confusing.

http://www.obamaftw.com/blog/gun-laws-restrictions/states-gun-laws-and-crime-across-the-united-states

[Gun Law Agnostic]

Great information here. The effects of gun legislation are difficult to tease out given the countless variables involved. It seems to me that things like poverty and income disparity combined with relatively easy access to guns are the reason the US sticks out like a sore thumb among advanced countries. http://www.factandmyth.com/gun-laws-restrictions/states-gun-laws-and-crime-across-the-united-states