A total return index measures investment performance through both price changes and reinvested cash distributions, such as bond coupons. This makes it suitable for estimating historical returns without omitting income. section 3.1.3
Corporate bond performance
A corporate bond analysis uses the BofA Merrill Lynch US Corporate 15+ Year Total Return Index, whose returns assume coupon reinvestment. Monthly data produce 9.67% average raw annual returns and 6.36% excess returns before adjusting for Treasury-yield changes. section 3.1.3
