Considering the infrequency of such bubbles in a single market, would it be valid to exclude test results from this period, or at least consider them seperately?
Another issue that I have is with the fact that the long-term bull market in US stocks began in 1980, and it's difficult to get data for individual stocks pre-dating this. I don't really feel comefortable that a test system designed exclusively around a long-term bull market will be valid going forward. On the other hand, even if I could get stock data from the '70s or earlier, would it be valid considering the structural changes to the markets over the past 20 years (ie. the internationalization, explosion of volume, etc.)?
I guess the central question is, how does one decide what data is most likely to be representative going forward? Perhaps an impossible question to answer.
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