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