Overlapping area represents the amount of risk that can be diversified away by holding Nasdaq and Greece TR in the same portfolio assuming nothing else is changed. The correlation between historical prices or returns on Greece TR and Nasdaq 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 Nasdaq are associated (or correlated) with Greece TR. Values of the correlation coefficient range from -1 to +1, where. The correlation of zero (0) is possible when the price movement of Greece TR has no effect on the direction of Nasdaq i.e. Nasdaq and Greece TR go up and down completely randomly.