My read of it was that the circles are centered on the date of the failure, and the stacking was some flavor of minimum height. The result is you get an approx

My read of it was that the circles are centered on the date of the failure, and the stacking was some flavor of minimum height. The result is you get an approximation of "area under the curve" of bank value that has failed, while retaining a sense of whether a particular peak was a few large actors, or a mound of tiny. I find that clear distinction valuable. The nice thing about Mike having posted the code is that, if you think there's a better way to portray it, the canvas is spread out before you. :)