PercentR is a momentum indicator used to gauge overbought and oversold
levels, and ranges between 0 and 100. However, unlike most other momentum
oscillators, the low end of the scale represents an overbought area, and the
high end an oversold condition. A reading of above 80 indicates oversold levels,
and below 20 indicates overbought. Williams %R has a tendency to peak ahead
of price, so it can be a good tool in identifying trend reversals.