Thursday, August 8, 2019

When Looking at Gun Ownership and Gun Deaths, Dates Matter



In response to the horrific shootings in El Paso, TX and Dayton, OH, I saw the graph below from Vox showing the correlation between gun ownership and gun deaths.  The graph was used on Late Night with Seth Meyers on Monday right after the shootings in the above clip.  It shows that the US is an extreme outlier in gun deaths and ownership comparred to other developed nations.
In response to the graph I was going to look at what type of a relationship still exists between guns and gun deaths after the US is excluded.  I went to the source for the data for this chart gunpolicy.org to find the data that was used in the its creation.  

The United States had 120.5 guns per 100 individuals and 12.21 total gun deaths per 100,000 individuals both in 2017.  On the graph the US is seen closer to 100 guns per 100 and below 12 deaths/100,000.

The United Kingdom or UK is in the lower left hand corner of the chart near the origin of both axes of the graphs.  The Gun Policy website for the UK lists 5.03 guns/100 for 2017 and 0.2 deaths/100,000 for the year 2015.  

The nation of Cyprus had 34 guns/100 for 2017 (the only time point listed) and 1 death/100,000 for 2016.  On the graph Cyprus is listed closer to 2 deaths/100,000 and closer to 40 guns/100.  

To do a proper correlational study, the data points for each county for each axis need to be from the same time point (year in this case).  There could be different ownership and death rates for the years not listed.  The investigator could be accused of cherry picking the data that supports the investigator's argument.  

I do agree with the argument that more guns lead to more gun deaths but to conduct a proper analysis of this data the methodology must be sound to protect against claims of dishonesty.  For me to do a proper study I will have to sift through the gun policy website and use only gun ownership and death data from a recent year for the countries from which both variables are available for that year.


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