Human nature

When you are trying to make sense of current events, the best way to do that is to look at how similar situations played out in the past. Considering that basic human nature is effectively the same as it has been, and various laws of nature and economics are the same, it would seem fairly easy to simply predict the future based upon the past.
Well as every prospectus in the world points out, past performance is no guarantee of the future. Why? Well the real problem is the interpretation of the past, and what comparison you make to the current situation.
I have seen a lot of comparisons between the current economic situation and the 1929 – 1940 period. If you are think they are comparable, it is easy to point out that after the initial drop in the stock market there were a number of significant rallies that didn’t take hold and led to greater and greater declines. Therefore, any upturn in the current market is not the start of a recovery, merely a “bear market rally”. Of course there have been many other notable recessions besides that one and they didn’t last as long or fall as far.
How can we know which one is most like this one, if any?
After the fact of course it is very easy for a statistician to find charts that show why the current situation was almost exactly like a prior one or more. Going the other way is clearly much more difficult, because however close your chart looks to a previous situation, it may not be as close a few months from now.
I do like looking at charts, especially since they are now are in color (I may be dating myself there). They also can provide a reasonable and somewhat rational approach to the future. Also, if everybody buys in to a particular indicator, it does become a reasonable predictor, because everyone buys into it.
Of course once that becomes predictable, some smart people figure out how to play it and the indicator becomes less useful for the majority. Like I said human nature hasn’t changed much if at all.