Quote from Tea:
Do trading patterns like turtle/Donchian 20-period breakouts stop being profitable because of over publicity of the pattern or because the supply vs. demand pressure ratio has changed and the pattern is no longer appropriate?
In the 60-70's bull market in commodities, the turtle method worked because there was strong demand for commodities in an inflationary time. When inflation's back was broken in the 80's there was less demand for commodities and breakout trading stopped working.
So is it the chicken or the egg? Was it the change in supply vs. demand or too many traders using the pattern?
I think its the change in the supply/demand pressure ratio. Example: during the internet boom when dot com stocks were in strong demand, the breakout strategy worked great. Then when traders and institutions loaded up on these stocks, there was less demand pressure than supply - result, breakout trading stopped working.
Being that traders usually lag in hopping on the trade pattern bandwagon - its easy for people to believe that over publicity is the reason a pattern stops working.
However, as stated above - I believe that the real reason is a shift in supply/demand pressure.