Why this ongoing crash is unique and unlike the 2008 crash

In the empirical sciences the so-called three-sigma rule of thumb expresses a conventional heuristic that nearly all values are taken to lie within three standard deviations of the mean, and thus it is empirically useful to treat 99.7% probability as near certainty.

— Subhadip Nandy (@SubhadipNandy) March 21, 2020