But people who trade against fundamentals aren&#x27;t trading <i>directly</i> against future profits, they are just betting on long term price movements.  HFT traders are betting on (very) short term price movements.<p>According to the theory that stock prices are a martingale (which is well established), there is no qualitative difference between long and short run price movements.  In particular, there is no reversion to the mean in stock prices [0].<p>[0] Of course, there are going to be literally hundreds of papers exhibiting some reversion to the mean effect.  But this effect is always tiny.