I take it that you are saying that the only practical sense in which this article would be useful would be if it helped one make money in the market. If it can't do that, it is worthless BS.
I also find value in models (and essays, pictures, cartoons, FR postings, ...) that seem to capture some element of where we are now, or what has happened so far, even if I can't just plug it into my Excel spreadsheet and retire to a South Pacific island next year.
Not every expression must guarantee profit to have worth.
Sure, mathematical models and charts can be mechanically extended to appear to predict future events. But in doing so, one is just showing where the model goes. The model itself does not predict when the model will break down, cease applying to reality. Sooner or later, they all break down.
And, post Black Friday of '29, the markets rallied ; that's right, they went up. It was Joe Kennedy and his little band of shorters, who, against the masses and masses of money being poured in, by the likes of Morgan, etc. created the backwash and did it ILLEGALLY ! This can no longer happen, BTW, since so many rules /laws have been changed since then.
One CAN make pots of money, if one knows that the market is going down and can guesstimate for how long.
A little factual history re THE SOUTH SEA BUBBLE. Yes, it was a BUBBLE, yes, the mania of the crowds ( as with ALL "BUBBLES" )fed it, what makes this one atypical, is that the Bank of England AND the government was involved in it, corruption was on a massive scale and it almost brought down the government, dethroned the monarchy, AND made a nation totally insolvent.
The nascent English Stock Exchange was so far removed from what was around in America, on Wall Street, in the 1920s, as to be almost totally unrecognizable.The swindles, that went down back then, make ENRON, Arthur Anderson, et al , look like kindergarten stuff, penny ante child's play. It even makes the dot.com stuff look honest .
What anyone, who finds the article "useful " should do, is to adjust their tinfoil.
Historically, excepting THE GREAT DEPRESSION ( more on that later ), our crashes/depressions ( we haven't had one since the that one )/resessions don't last all that long. The above chart, is therefore misleading to utterly bogus. The ONLY reasons that the one sort of begun in '29 lasted as long as it did, was because there was a worldwide depression, which was the direct aftermath of WW I and the Treaty of Versailles, Wilson's inepttitude, the Taft-Hartley garbage, and the rise of Hitler; not to mention FDR's Socialistic stupidities.
Oh yes, and the authors of the charts, based at least some of it, on charts from the CBOE ( Chicago Board Otions Exchange ), whose charts do NOT relate to ALL markets; not even in general. Since I am probably the ONLY person on FR ( well, the only one who types to it ... LOL ) who happens to be part of a company that is a FOUNDING member of the CBOE, I am also the ONLY one on this thread, who is talking about something they actually know about.