Börsenlexikon: Korrelation

In finance, correlation is a statistical measure of how two securities move in relation to each other. Correlations are used in advanced portfolio management. A correlation is calculated at what is called the correlation coefficient, which varies between -1 and +1. A perfect positive correlation (a correlation coefficient +1) implies when one security moves, either up or down, the other security will move in lockstep in the same direction. Alternatively, perfect negative correlation means if one security moves in either direction, the security that is perfectly negatively correlated will move an equal amount in the opposite direction. If the correlation is 0, the securities' movements are said to have no correlation; they are completely random. In real life, perfectly correlated securities are rare; you are more likely to find securities with some degree of correlation.