Profitable ETF Trading Strategies: understanding Williams%R, a simple oscillator
Oscillators are tools of technical analysis that are used to identify periods of time when price can be considered in an overbought or oversold condition. The overbought and oversold conditions are found at the extremes which vary based on how the oscillator is constructed. Some oscillators look exclusively at price with respect to the range of high and low in the look back period. Others incorporate some measures of statistical description. In most cases, the look back period is required in order to establish what may be considered normal and extreme for the price channel.
Depending on the market condition, your strategy could be one of channel trading in which case you expect price to reverse once it’s in this extreme condition or to prepare yourself for breakout trades in which case you expect price to continue explosively through this extreme moment and breakout of the channel.
Williams%R is my favorite oscillator that can be found in all charting packages, because it is the simplest one to understand and is very visual. Created by Larry Williams, the famous technical analyst, this indicator creates an index ranging from zero to -100 for the look back period. An index score of zero is assigned to the highest high of the look back period and a score of -100 is assigned to the lowest low. The look back period is then segmented into 100 equal sections and the oscillator value of price is interpolated.
Readings between zero and -20 are considered to be overbought because they are in the top 20% of price, whereas readings between -80 and -100 are considered to be oversold because they are in the bottom 20% of price during the look back period. Readings between -20 and -80 are considered to be in the normal range of the channel.
I have a trading belief that volatile moves are more likely to occur when price is at an extreme reading either overbought or oversold, and so this oscillator alligns very nicely with my trading believes and is therefore useful for me to help classify market conditions. I use it to help me assess for stalking. It leads me to study assets that I believe are likely to make a vigorous move in the short term.
The only problems that I have with Williams%R are that the scale of zero to -100 is not intuitive and that it includes today’s price action in the index. These are only small problems however and for most of my screening filters I find that it works just fine.
I typically examine a look back period of 10 days and one year because both of those time periods are useful for the way that I trade.