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