My experience has been that successful investing is about finding a simple strategy that works, and then having the patience and discipline to stick with it - even when it is not performing in the short term.
Over short periods of time, randomness has a bigger influence. A lot of investors get impatient, and they then abandon the system and switch to trying something else.
With hedge funds and mutual funds, a lot of it is about needing good short term results to attract new money, so they keep trying complicated stuff to avoid any down performances - this helps keep them from getting good long-term results.
On my blog, I wrote about a book called "The Hedge Fund Mirage", which is critical of that whole industry:
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