jobowker said: Can someone explain the difference between the two mass shooting lines for me? I'm not sure what a smoothing algorithm entails. Click to expand...

The dotted line is the actual number of casualties. Theres such a difference from one year to the next, the line bounces up and down like someone having a heart attack. If you take an average of those numbers and plot a line (green), it is smoother and easier for the eye to visualize the overall trend, whether its going up or down. Thats the basic idea at least.