expected default and loss rates of Aaa issuers are lower on average than those of Aa at all horizons, and Aa loss and default rates are lower than single A at all horizons, etc. PDRs will use the same rating scale used to rate long-term securities and CFRs, with the exception that a new Using the same figures from the scenario above, but assuming only a 50% probability of default, the expected loss calculation equation is: LGD (20%) X probability of default (50%) X exposure at To calculate a cumulative return, you need two pieces of data: the initial price, Pinitial, and the current price, Pcurrent (or the price at the end date of the period over which you wish to calculate the return). The cumulative return is equal to your gain (or loss!) as a percentage of your original investment.