The UK Guardian newspaper recently published an interactive ring diagram showing gun regulation by US states. It’s an attractive diagram but makes so many elementary mistakes in charting that it fails to summarize the data in a meaningful way.
Analysis: If the graph makes a single point, it’s that all states regulate whether a weapon is carried in public or not, but the Northeast is the most highly regulated area for guns, while Southeast is the least. Beyond that, it’s not clear what the point of the graph is — how does the user learn more by interacting with the graphic? What are the subtle points of understanding does the user get from the diagram?
Looking closer at the graphic, I find a lot of problems with the execution:
- The categories are heterogeneous: carry in public is one type of regulation vs. what type of gun requires a permit vs. data points on what is regulated (missing firearms, locking devices and points of sales (gun shows, private sales). For regulation, these seem like a jumble of unrelated issues stuffed into one category. The categorization is the most sloppy part of this graph and does not add to the understanding of the issues.
- The underlying data is poorly documented, although there is a companion post as to how the creators struggled to summarize the data (ie fit the data to the visualization they were attempting. There is also a lot missing to annotate methodology: when the graph is scaled by population, is the outermost ring proportional? or entire slice? what’s the relevance of “population”? Wouldn’t it have made more sense to have the slices proportional to gun owners? What is the time frame for the data? Is there a data table and a clear methodology?
- Color choice seems arbitrary and changes for each data category. Does red mean “unrestricted” when referring to regulation but “concealed carry” permitted?
How the chart could be improved:
- Clearly define what the point of the visualization is. Is it to show that there are geographic differences in gun laws? Show how gun regulation impacts states with higher populations? Show that states with fewer gun laws have more/less violent crimes committed with guns?
- Consistent categorization scheme and color scheme. a two tiered category of gun types (hand guns, rifles, etc) and channels (gun shows, gun shops, and private sales) with a simple scale (white= unregulated, light blue = partial regulation, dark blue = full regulation)
- Add a data table and a clear description of methodology used for categorization and how the data fits the categories.
Overall, I like the idea for this graph to display multiple dimensions, but think it is too muddled to provide any insights.