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