This screen finds stocks whose price has just crossed below the middle Bollinger Band, the 20-day moving average. Bollinger Bands(20,2), created by John Bollinger, plot a 20-day simple moving average as the middle band and upper and lower bands two standard deviations away, so the bands widen when volatility rises and narrow when it falls. Moving below the 20-day average shows that the short-term trend has turned down, with the lower band as the next target.
