This screen finds stocks whose price has just crossed below the lower Bollinger Band. 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. A move outside the lower band shows strong selling; it can start a band walk lower in a strong downtrend or mark a short-term oversold extreme.
