We are living in the golden age of Bollinger Band Squeeze.
A Bollinger Band is a visual representation of Standard Deviation. The outer solid blue lines in the chart below represent the 2 standard deviation location, as compared to the middle line, which is a moving average.
A Bollinger Band Squeeze is when the distance from top to bottom of the blue lines is relatively small. This indicates “building pressure” and (often) results in an explosive movement outside of the lines.
As you can see this has consistently been the case in the main indexes for most of the last year. This has not always such a good indicator in the past, and by itself it does not tell you when exactly the next big move is going to happen, but in conjunction with a reasonable OTM-option buying strategy, it should have return-enhancing potential.