Spread that solely mirrors credit risk
Based on historical data on defaults we can derive the fraction of the spread over riskless bonds for different rating classes and maturities, that is solely due to the probability of default and loss given default. The expected loss rate is derived from these two factors. Market participants who have a buy-and-hold perspective must decide on whether the current spread of a corporate bond sufficiently compensates for default and migration risk.
This is rather the perspective of a private than an institutional investor, because the latter in general has a short- to medium-term investment horizon and rarely holds a bond to maturity. In general, the institutional investor tries to achieve an excess return against a benchmark with a trading oriented management approach.
However, for the calculation of the required spread from a buy-and-hold perspective reliable default probabilities and recovery rates have to be used. If the issuer has an agency rating, Moody’s historical database is a good starting point. This database compiles expected default probabilities on a historical basis which is updated annually and also average recovery rates depending on the seniority of a bond. Those values allow to calculate a “fair” spread that solely mirrors credit risk.
One example from the automotive sector is the large spread differential between Ford and Renault bonds with similar coupon and maturity.
Despite the wide dispersion of credit spreads within the rating buckets the general link between credit spreads and ratings is clear, with average spread increasing as credit quality decreases. However, as it illustrates there are large overlaps between individual rating distributions. Myriad examples can be found to show that market participants often perceive the risk of one company in comparison to another to be completely different, even if both have the same rating. It should be noted that it includes bonds with rather different maturities and coupons.