I realised that I’d never written an explainer for the work I did at the Guardian Datablog in December, so here we go.
The first piece I did for them was to do with the AR-15 rifle. On Friday December 14 2012, Adam Lanza used an AR-15 rifle as he killed his mother, six teachers and twenty children in Newtown. At the Guardian we were interested in this particular weapon and how widely available it was in the United States. The massacre had reopened the perennial debate on US gun control laws and the availability of guns to US citizens. We wanted to know how many there were in the US.
The data we had came from the American Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) in PDF hard copy format.
We had to find the data about AR-15 rifles within that data, clean it and input it into a Google spreadsheet. For example, “Smith & Wesson” would sometimes appear as “Smith and Wesson”, which needed to be corrected before we could analyse and visualise it. We also found authoritative sources on exactly what an AR-15 rifle does and its capabilities.
We subtracted the number of exported AR-15s to arrive at the best figure for the rifles inside the United States. We found the overall trend was a decline in the number of AR-15s in the US and that Smith & Wesson made the most rifles that stayed in America.