Overlapping area represents the amount of risk that can be diversified away by holding OMX COPENHAGEN and Stockholm in the same portfolio assuming nothing else is changed. The correlation between historical prices or returns on Stockholm and OMX COPENHAGEN is a relative statistical measure of the degree to which these equity instruments tend to move together. The correlation coefficient measures the extent to which returns on OMX COPENHAGEN are associated (or correlated) with Stockholm. Values of the correlation coefficient range from -1 to +1, where. The correlation of zero (0) is possible when the price movement of Stockholm has no effect on the direction of OMX COPENHAGEN i.e. OMX COPENHAGEN and Stockholm go up and down completely randomly.