I've been trading the model, without stops, and feeling the pain lately.
I am not blaming anyone...it was my decison not to use stops. I think, however,
that the limitation of a quant model is that it cannot function in a news-driven
market, as asset prices are governed primarliy by factors not reflected in the
model. Occasionally prices anticipate the news (as in earnings announcements),
but no model could have known about Fannie, Freddie, LEH, the failed bailout
vote, the bailout vote, and the global rate cut.
Because the market is at the mercy of late breaking news, you need to
set stops. I use them most of the time, and when I don't, I will buy call or
put options to reduce risk.
Your comments about
a news-driven market are very true. If this condition existed all
the time, we could not predict anything. Fortunately, it doesn't.