A few days after the mass shooting in Connecticut, Dr. A. Charles Catania sent us a graph of the 12 deadliest mass shootings in the United States. He showed their effects cumulatively, over time, so that you could see how steep the slope has become in recent years. Since then, a number you have asked whether there is any conclusion to be drawn from the long break in points on the curve, which is to say, the long break in the list of America's deadliest shootings.
By way of an answer, Dr. Catania, a behavioral and experimental psychologist, updated his chart to show the period covered by the federal ban on assault weapons -- 1994 to 2004. He writes:
Here is a new version of my earlier graph on cumulative deaths in mass shootings. In a cumulative display, each data point always includes the total of all the previous entries. The advantage of this kind of display is that the steepness of the line gives a rate, so if one portion is fairly flat and another is fairly steep, the rate for the first part is low and the rate for the second part is high.
The graph is similar to the one I presented before, but now the added shaded area shows the automatic weapons ban. The rate was increasing (the graph was getting steeper) until the ban went into effect. Then it flattened out, but after the ban ended the rate became steeper still. If it keeps going that way, 2013 will not be a good year.
I hope others will try graphing other data for automatic weapons deaths (for example, when they are used in drive-by shootings) to see if the same effect of the ban shows up for other kinds of shooting deaths.
There is no single cause for events like these, so of course it is true that they are only one factor. But if, among multiple causes such as first-person shooter games, a culture of violence, insufficient mental health resources, etc., automatic weapons are a contributing factor, so that they are enough to drive just the occasional individual over the threshold for committing another atrocity like the one that happened in Newtown, no pleading by the gun lobby that only people kill people is acceptable.
Thanks for the new chart, Dr. Catania. (How to send us stuff.)