Overlapping area represents the amount of risk that can be diversified away by holding AEX Amsterdam and EURONEXT BEL-20 in the same portfolio assuming nothing else is changed. The correlation between historical prices or returns on EURONEXT BEL-20 and AEX Amsterdam 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 AEX Amsterdam are associated (or correlated) with EURONEXT BEL-20. Values of the correlation coefficient range from -1 to +1, where. The correlation of zero (0) is possible when the price movement of EURONEXT BEL-20 has no effect on the direction of AEX Amsterdam i.e. AEX Amsterdam and EURONEXT BEL-20 go up and down completely randomly.