Bollinger's Bandwith Indicator is used to warn of changes in volatility. As we know from using Bollinger Bands, a squeeze where the bands converge into a narrow neck often precedes a rapid rise in volatility. A Bollinger Band squeeze is highlighted by a fall in the Band Width indicator to below 2.0%. Bollinger claims that a drop below 2% on the S&P 500 has led to many spectacular moves, but warns that the market often starts with a fake move, in the wrong direction, before the real move commences. Goldman Sachs is displayed with 20-day Bollinger Band Width.