Autocorrelation is a statistical tool used to measure the degree of similarity between a given time series and a lagged version of itself over successive time intervals. On some occasions, the past performance for a certain security can serve as an indication of future movements. By identifying and measuring the degree of correlation between a security’s past and present values, technical analysts can better understand how future prices are likely to behave based on the previously observed trends and patterns.

An autocorrelation is a statistic that measures the relationship between a variable’s current value and its past values. A perfect autocorrelation value of +1 indicates a strong positive correlation and a perfect autocorrelation of -1 characterizes a strong negative correlation between a security’s historic and current values. Autocorrelation values outside of this range can still indicate a correlation, albeit one that is weaker than either the perfect positive or negative correlations.

Overall, autocorrelation provides an opportunity for traders to understand and predict future market movements by looking at past price action. By measuring the historical correlations of a stock’s current value with its previous values, technical analysts can gain better insight into how much influence past prices have on future prices. Autocorrelation can also help to identify which particular periods of historical performance have the most influence on future movements. By deducing this information, traders can better assess whether a stock is experiencing true price trend changes or merely reverting back to previously identified patterns. Hence, autocorrelation helps to improve traders’ long and short-term forecasting capabilities.