      As explained in the Correlation Coefficients chapter, there is a timedelay in price action between even the most highly correlated stocks. Forexample, knowing that there is bullish pressure in the entire sector, youcan use the larger stocks in the sector in the same way that you use theTicks or the S&P Futures as a forward-looking indicator. There are always ahandful of primary stocks that drive a sector. Using the correlationsbetween these stocks, and knowing the time lags between the stocks in thesector, it is possible to trade a sector on the long and short side, day inand day out.