FN415.13 1
Measuring Actuarial Default Risk (b)
Measuring Actuarial Default Risk (b)
Cumulative Default Rate
This is the proportion of issuers rated R that
FN415.13 5 Average Default Rate
We can express the total cumulative default rate as an
average) per period default rate d, by setting
As we move from annual to semiannual and
ultimately continuous compounding, the average default rate becomes
Where da, ds , dc are default rates using annual,
Example: Computing Cumulative default probability
Consider a B-rated firm that has default rates of
d1 = 5%, d2 = 7%. Compute the cumulative default probabilities.
In the first year, k1 = d1 = 5%. After one year, the survival rate is S1 = 0.95. The probability of
defaulting in year 2 is then
k2 = S1 x d2 = 0.95 x 0.07 = 6.65%.
After two years, the survival rate is
(1 – d1) (1 – d2) = 0.95 x 0.93 = 0.8835.
Thus, the cumulative probability of defaulting in
years 1 and 2 is
FN415.13 7 Transition Probabilities
The transition matrix gives the probability of
moving to one rating conditional on the rating at the beginning of the period.
The usual assumption is that these moves follow a
Transition Matrix
In year 1, with probability
D[t1 | B(t0)] = P(D1 | B0) = 3%
In year 2, after going from B to A in the first year,
then A to D in the second; or from B to B, then to; or from B to C, then to D.
The default probability is
P(D2| A1).P(A1) + P(D2| B1).P(B1) + P(D2| C1).P(C1) = (0.00 x 0.02) + (0.03 x 0.93) + (0.23 x 0.02) = 3.25%.
The cumulative probability of default over the two
years is then
Time Variation in Default Probabilities
Defaults are also correlated with economic
activity. Moody's, for example, has compared the annual default rate to the level of industrial
production since 1920.
Moody's reports a marked increase in the default
rate in the 1930s at the time of the Great Depression and during the recent recessions.
These default rates, however, do not control for
structural shifts in the credit quality.
Recent years, many issuers came to the market
Recovery Rates
Credit risk also depends
on the loss given default
(LGD). This can be
measured as 1 minus the
recovery rate
or fraction
FN415.13 15 The Bankruptcy Process
Normally default is a state that affects all
obligations of an issuer equally especially
when accompanied by a bankruptcy filing. In most
countries, formal bankruptcy process provides a centralized forum for resolving all the claims
against the corporation.
The bankruptcy process creates a pecking order
for a company's creditors.
This spells out the order in which creditors are
FN415.13 17 Estimates of Recovery Rate
Recovery rates are commonly estimated
from the market prices of defaulted debt
shortly after default.
This is the best estimate of the future
recovery
It takes into account the value of the
firm's assets, the estimated cost of the
bankruptcy process, and various means
of payment (e.g., using equity to pay
Factors affecting Recovery Rate
The status or seniority of the
debtor.
The state of the economy
The obligor’s characteristics
FN415.13 21 Trading Prices vs Discounted recovery rate
The evidence, however, is that trading prices are, on
average lower than the discounted recovery rate.
The averaged is counted recovery rate is systematically
higher than the indication given by trading prices.
This creates an interesting trading opportunity. Buying
the defaulted debt and working through the recovery process should create value.
Indeed, this largely explains the existence of the
hedge fund category called distressed securities funds.
Such funds invest in selected distressed securities and
Assessing Corporate Rating