It is an indicator used by traders to judge a security's long-term trend by comparing bars which comprise its closing,   opening, high and low prices during a specific period of time. When the ASI is positive, it recommends that the long-term trend will be higher, and when the ASI is negative, it recommends that the long-term trend will be lower. 

The ASI is given by Welles Wilder.

While the ASI is most commonly used for futures trading, it can also be used for evaluating the price trends of other assets. The ASI can be used in combination with price charts so as to confirm trendline breakouts, because the same trendline would be piercing in both situations.