The Efficiency Ratio (ER) was first presented by Perry Kaufman in his 1995 book ‘Smarter Trading‘.  It is calculated by dividing the price change over a period by the absolute sum of the price movements that occurred to achieve that change.  The resulting ratio ranges between 0 and 1 with higher values representing a more efficient or trending market.

The value of the ER ranges between 0 and 1. It has the value of 1 when prices move in the same direction for the full time over which the indicator is calculated, e.g. n bars period. It has a value of 0 when prices are unchanged over the n periods. When prices move in wide swings within the interval, the sum of the denominator becomes very large compared to the numerator and ER approaches zero.

Some uses for ER:
– A qualifier for a trend following trade; a trend is considered “persistent” only when RE is above a certain value, e.g. 0.3 or 0.4 .
– A filter to screen out choppy stocks/markets, where breakouts are frequently “fakeouts”.
– In an adaptive trading system, helping to determine whether to apply a trend following algorithm or a mean reversion algorithm.
– It is used in the calculation of Kaufman’s Adaptive Moving Average (KAMA).