Since the terms "recession" and "depression" first started making headlines in late 2007 (+/-) I've watched with horror as countless traders, analysts, flapping heads, journalists and other market participants blindly extrapolate historical patterns and apply them to our current situation. The most recent example I've seen (and my apologies as this is nowhere near the worst I've seen), is over at Clusterstock where Henry Blodget quotes Merrill strategist David Rosenberg (who, in fairness, actually includes some caveats):
It was extremely difficult for equity investors to make money in the decade following the June 1932 bottom. After the three-month rally (+75%) off the bottom in 1932, equity markets were extremely volatile and largely sideways for the next nine years. Keep in mind that the jury is still out as to whether the March 2009 lows were in fact the bottom, as was the case in 1932.
Generally, we find such failed "analysis" takes the form of:
"In 19xx, the ____ Index dropped __ % over __ months, _________ economic indicators were _________, so judging from history, we conclude that now, we should expect X, Y and Z..."
Now, were conditions today exactly, or at least mostly the same as they were during previous recessions/depressions, I could see how this sort of analysis might make sense. Contrary to the claims of others, I think its quite clear that global (and regional) dynamics and fundamentals are materially different than they have been at any earlier period of human history, which means these analyses constitute at least one type of logical fallacy, and are thus of little or dubious value. No doubt, I'm guilty of some of these myself, but that's another story altogether.
I won't go so far as to claim that such claims are useless, since they may reveal some information about investor behavior and psychology, which is for the most part unchanged over at least the past few centuries. However, this is hardly a redeeming quality of these poorly conceived - and even more-poorly used - forms of analysis.
No doubt both those who present and heed these arguments are suffering from at least one form of cognitive bias, although both are similarly blissfully ignorant of their own psychological predispositions and the like.
I'm of the belief that such forms of analysis - and those who propagate their use - do more harm than good insofar as almost any conclusion reached is, at best, a non sequitur, and may introduce or reinforce false beliefs to the investor population.
Alas, despite the painfully obvious errors inherent in such comparisons, I still see them far-too frequently, in places and from people who should know better.
Tip of the hat to those who avoid such poor analysis, wag of the finger to those who don't!