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