Note: The 1873 crash was called the "long depression"; 1920/21 was the crash that I was referring to in terms of both its violence and subsequent recovery -- and which, if you look around the web at investment commentary, you won't find mentioned.  Wholesale prices fell by nearly 40% and industrial output by roughly a third.  But it was nonetheless real -- and so fast that nobody called it a Depression, simply because it didn't last long enough -- and the recovery posted a productivity increase of sixty percent on the back side of it.  As with all large dislocations it came about mostly the result of speculation as was 1873, coupled with the realignment of the economy at the end of WWI -- and then a demand shock from the 1918 flu pandemic.