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