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