bond and cds pricing with stochastic recovery : moody's...
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Bond and CDS Pricing with Stochastic Recovery :Moody’s PD-LGD Correlation Model
Albert Cohen
Actuarial Sciences ProgramDepartment of Mathematics
Department of Statistics and ProbabilityC336 Wells Hall
Michigan State UniversityEast Lansing MI
[email protected]@stt.msu.edu
http://actuarialscience.natsci.msu.edu
SFU Actuarial Seminar - June 2014
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 1 / 42
Outline
1 Review of Some Structural ModelsFundamentals of Structural ModelsMerton ModelBlack-Cox ModelMoody’s KMV Model
2 Stochastic RecoveryComplete Recovery ModelPartial Recovery ModelCorrelated Asset-Recovery ModelBond Price - 2d Black-Cox ModelCDS - 2d Black-Cox ModelConclusions
Joint work with Nick Costanzino (nick [email protected], OTPP and
U of Toronto - RiskLab)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 2 / 42
Single-Name Default Models
Single-name default models typically fall into one of three main categories:
Structural Models. Attempts to explain default in terms offundamental properties, such as the firms balance sheet and economicconditions (Merton 1974, Black-Cox 1976, Leland 1994 etc).
Reduced Form (Intensity) Models. Directly postulates a model forthe instantaneous probability of default via an exogenous process λt(Jarrow-Turnbul 1995, Duffie-Singleton 1999 etc) via:
P[τ ∈ [t, t + dt)|Ft ] = λtdt
Hybrid Models. Incorporates features from structural andreduced-form models by postulating that the default intensity is afunction of the stock or of firm value (Madan-Unal 2000,Atlan-Leblanc 2005, Carr-Linetsky 2006 etc).
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 3 / 42
Single-Name Default Models
Single-name default models typically fall into one of three main categories:
Structural Models. Attempts to explain default in terms offundamental properties, such as the firms balance sheet and economicconditions (Merton 1974, Black-Cox 1976, Leland 1994 etc).
Reduced Form (Intensity) Models. Directly postulates a model forthe instantaneous probability of default via an exogenous process λt(Jarrow-Turnbul 1995, Duffie-Singleton 1999 etc) via:
P[τ ∈ [t, t + dt)|Ft ] = λtdt
Hybrid Models. Incorporates features from structural andreduced-form models by postulating that the default intensity is afunction of the stock or of firm value (Madan-Unal 2000,Atlan-Leblanc 2005, Carr-Linetsky 2006 etc).
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 3 / 42
Single-Name Default Models
Single-name default models typically fall into one of three main categories:
Structural Models. Attempts to explain default in terms offundamental properties, such as the firms balance sheet and economicconditions (Merton 1974, Black-Cox 1976, Leland 1994 etc).
Reduced Form (Intensity) Models. Directly postulates a model forthe instantaneous probability of default via an exogenous process λt(Jarrow-Turnbul 1995, Duffie-Singleton 1999 etc) via:
P[τ ∈ [t, t + dt)|Ft ] = λtdt
Hybrid Models. Incorporates features from structural andreduced-form models by postulating that the default intensity is afunction of the stock or of firm value (Madan-Unal 2000,Atlan-Leblanc 2005, Carr-Linetsky 2006 etc).
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 3 / 42
Single-Name Default Models
Single-name default models typically fall into one of three main categories:
Structural Models. Attempts to explain default in terms offundamental properties, such as the firms balance sheet and economicconditions (Merton 1974, Black-Cox 1976, Leland 1994 etc).
Reduced Form (Intensity) Models. Directly postulates a model forthe instantaneous probability of default via an exogenous process λt(Jarrow-Turnbul 1995, Duffie-Singleton 1999 etc) via:
P[τ ∈ [t, t + dt)|Ft ] = λtdt
Hybrid Models. Incorporates features from structural andreduced-form models by postulating that the default intensity is afunction of the stock or of firm value (Madan-Unal 2000,Atlan-Leblanc 2005, Carr-Linetsky 2006 etc).
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 3 / 42
Single-Name Default Models
Single-name default models typically fall into one of three main categories:
Structural Models. Attempts to explain default in terms offundamental properties, such as the firms balance sheet and economicconditions (Merton 1974, Black-Cox 1976, Leland 1994 etc).
Reduced Form (Intensity) Models. Directly postulates a model forthe instantaneous probability of default via an exogenous process λt(Jarrow-Turnbul 1995, Duffie-Singleton 1999 etc) via:
P[τ ∈ [t, t + dt)|Ft ] = λtdt
Hybrid Models. Incorporates features from structural andreduced-form models by postulating that the default intensity is afunction of the stock or of firm value (Madan-Unal 2000,Atlan-Leblanc 2005, Carr-Linetsky 2006 etc).
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 3 / 42
What Exactly Are Structural Models Supposed To Do?
Price both corporate debt and equity securities (perhaps evenequity derivatives and CDS!) Important for buyers/investors,sellers/firms, and advisors
Estimate default probabilities of firms. Useful to commercialbanks, investment banks, rating agencies etc.
Determining optimal capital structure decisions. Essential part ofeconomic capital estimation (Moody’s Portfolio Manager andRiskFrontier)
Analyzing most corporate decisions that affects cash flows. Canaid in determining most value-maximizing decisions
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 4 / 42
What Exactly Are Structural Models Supposed To Do?
Price both corporate debt and equity securities (perhaps evenequity derivatives and CDS!) Important for buyers/investors,sellers/firms, and advisors
Estimate default probabilities of firms. Useful to commercialbanks, investment banks, rating agencies etc.
Determining optimal capital structure decisions. Essential part ofeconomic capital estimation (Moody’s Portfolio Manager andRiskFrontier)
Analyzing most corporate decisions that affects cash flows. Canaid in determining most value-maximizing decisions
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 4 / 42
What Exactly Are Structural Models Supposed To Do?
Price both corporate debt and equity securities (perhaps evenequity derivatives and CDS!) Important for buyers/investors,sellers/firms, and advisors
Estimate default probabilities of firms. Useful to commercialbanks, investment banks, rating agencies etc.
Determining optimal capital structure decisions. Essential part ofeconomic capital estimation (Moody’s Portfolio Manager andRiskFrontier)
Analyzing most corporate decisions that affects cash flows. Canaid in determining most value-maximizing decisions
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 4 / 42
What Exactly Are Structural Models Supposed To Do?
Price both corporate debt and equity securities (perhaps evenequity derivatives and CDS!) Important for buyers/investors,sellers/firms, and advisors
Estimate default probabilities of firms. Useful to commercialbanks, investment banks, rating agencies etc.
Determining optimal capital structure decisions. Essential part ofeconomic capital estimation (Moody’s Portfolio Manager andRiskFrontier)
Analyzing most corporate decisions that affects cash flows. Canaid in determining most value-maximizing decisions
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 4 / 42
What Exactly Are Structural Models Supposed To Do?
Price both corporate debt and equity securities (perhaps evenequity derivatives and CDS!) Important for buyers/investors,sellers/firms, and advisors
Estimate default probabilities of firms. Useful to commercialbanks, investment banks, rating agencies etc.
Determining optimal capital structure decisions. Essential part ofeconomic capital estimation (Moody’s Portfolio Manager andRiskFrontier)
Analyzing most corporate decisions that affects cash flows. Canaid in determining most value-maximizing decisions
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 4 / 42
How Do We Mathematically Define Default?
Several possible triggers for default:
Zero Net Worth Trigger. Asset value falls below debt outstanding.But... firms often continue to operate even with negative networth. Might issue more stock and pay coupon rather thandefault.
Zero CashflowTrigger. Cashflows inadequate to cover operating costs.But... zero current net cash flow doesn’t always imply zeroequity value. Shares often have positive value in thisscenario. Firm could again issue more stock rather thandefault.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 5 / 42
How Do We Mathematically Define Default?
Several possible triggers for default:
Zero Net Worth Trigger. Asset value falls below debt outstanding.But... firms often continue to operate even with negative networth. Might issue more stock and pay coupon rather thandefault.
Zero CashflowTrigger. Cashflows inadequate to cover operating costs.But... zero current net cash flow doesn’t always imply zeroequity value. Shares often have positive value in thisscenario. Firm could again issue more stock rather thandefault.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 5 / 42
How Do We Mathematically Define Default?
Several possible triggers for default:
Zero Net Worth Trigger. Asset value falls below debt outstanding.But... firms often continue to operate even with negative networth. Might issue more stock and pay coupon rather thandefault.
Zero CashflowTrigger. Cashflows inadequate to cover operating costs.But... zero current net cash flow doesn’t always imply zeroequity value. Shares often have positive value in thisscenario. Firm could again issue more stock rather thandefault.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 5 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]
This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Simplest Framework for Structural Models
Assume that the firm’s assets At is the sum of equity Et and debt Dt .
Assumptions on the assets process must be postulated.
Assumptions on the debt structure must be postulated.
A default mechanism τ and payout structure f (Aτ , τ) must bepostulated.
The main idea, pioneered by Merton, is that the firms equity Et isthen modeled as a call option on the assets At of the firm at expiry T :
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]This connects equity Et with debt value Dt . In particular if Dt has atractable debt structure it provides a methodology to compute defaultprobability, bond price, credit spreads, recovery rates, etc.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 6 / 42
Merton Model Set-up
Assume a probability space (Ω,F ,P)
Underlying asset is modeled as GBM under Physical Measure P:
dAt = µAAtdt + σAAtdW At
Default is implicitly assumed to coincide with the event
AT < B
:
τMerton = T 1AT<B +∞1AT≥B
This results in a turnover of the company’s assets to bondholders ifassets are worth less than the total value of bond outstanding.
At maturity the bond value (payoff) is:
payoffMerton = BT = AT1τ=T + B1τ=∞
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 7 / 42
Merton Model Set-up
Assume a probability space (Ω,F ,P)
Underlying asset is modeled as GBM under Physical Measure P:
dAt = µAAtdt + σAAtdW At
Default is implicitly assumed to coincide with the event
AT < B
:
τMerton = T 1AT<B +∞1AT≥B
This results in a turnover of the company’s assets to bondholders ifassets are worth less than the total value of bond outstanding.
At maturity the bond value (payoff) is:
payoffMerton = BT = AT1τ=T + B1τ=∞
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 7 / 42
Merton Model Set-up
Assume a probability space (Ω,F ,P)
Underlying asset is modeled as GBM under Physical Measure P:
dAt = µAAtdt + σAAtdW At
Default is implicitly assumed to coincide with the event
AT < B
:
τMerton = T 1AT<B +∞1AT≥B
This results in a turnover of the company’s assets to bondholders ifassets are worth less than the total value of bond outstanding.
At maturity the bond value (payoff) is:
payoffMerton = BT = AT1τ=T + B1τ=∞
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 7 / 42
Merton Model Set-up
Assume a probability space (Ω,F ,P)
Underlying asset is modeled as GBM under Physical Measure P:
dAt = µAAtdt + σAAtdW At
Default is implicitly assumed to coincide with the event
AT < B
:
τMerton = T 1AT<B +∞1AT≥B
This results in a turnover of the company’s assets to bondholders ifassets are worth less than the total value of bond outstanding.
At maturity the bond value (payoff) is:
payoffMerton = BT = AT1τ=T + B1τ=∞
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 7 / 42
Merton Model Set-up
Assume a probability space (Ω,F ,P)
Underlying asset is modeled as GBM under Physical Measure P:
dAt = µAAtdt + σAAtdW At
Default is implicitly assumed to coincide with the event
AT < B
:
τMerton = T 1AT<B +∞1AT≥B
This results in a turnover of the company’s assets to bondholders ifassets are worth less than the total value of bond outstanding.
At maturity the bond value (payoff) is:
payoffMerton = BT = AT1τ=T + B1τ=∞
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 7 / 42
Merton Model Bond Price
Consequently,
Bt = e−r(T−t)Et [BT ] = e−r(T−t)Et [AT1τ=T + B1τ=∞]
= e−r(T−t)
[∫ B
0A · Pt [AT ∈ dA] + B
∫ ∞B
Pt [AT ∈ dA]
]= e−r(T−t)Et [AT | AT < B] · Pt [AT < B] + e−r(T−t)B · Pt [AT ≥ B]
= Be−r(T−t) − e−r(T−t)Et [(B − AT ) | AT < B] · Pt [AT < B]
:= Be−r(T−t) − Be−r(T−t)Et [Loss | Default] · Pt [Default].
Here, Loss denotes the loss per unit of face in the event
AT < B.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 8 / 42
Merton Model Bond Price
Consequently,
Bt = e−r(T−t)Et [BT ] = e−r(T−t)Et [AT1τ=T + B1τ=∞]
= e−r(T−t)
[∫ B
0A · Pt [AT ∈ dA] + B
∫ ∞B
Pt [AT ∈ dA]
]= e−r(T−t)Et [AT | AT < B] · Pt [AT < B] + e−r(T−t)B · Pt [AT ≥ B]
= Be−r(T−t) − e−r(T−t)Et [(B − AT ) | AT < B] · Pt [AT < B]
:= Be−r(T−t) − Be−r(T−t)Et [Loss | Default] · Pt [Default].
Here, Loss denotes the loss per unit of face in the event
AT < B.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 8 / 42
Merton Model PD and LGD
BMertont,T = Be−r(T−t)N (d2) + AtN (−d1)
PDMerton = Pt [AT < B] = N (−d2)
LGDMerton =1
BEt [B − AT |AT < B] = 1− er(T−t) At
B
N (−d1)
N (−d2)
d1 =ln(At/B) + (r + 1
2σ2A)(T − t)
σA√
T − t= d+
d2 =ln(At/B) + (r − 1
2σ2A)(T − t)
σA√
T − t= d−
(1)
Real-world probabilities from risk-neutral probabilities via µ→ r (WangTransform:)
PDPMerton = N(N−1(PDQMerton)− µA − r
σA
√T
)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 9 / 42
Merton Model PD and LGD
BMertont,T = Be−r(T−t)N (d2) + AtN (−d1)
PDMerton = Pt [AT < B] = N (−d2)
LGDMerton =1
BEt [B − AT |AT < B] = 1− er(T−t) At
B
N (−d1)
N (−d2)
d1 =ln(At/B) + (r + 1
2σ2A)(T − t)
σA√
T − t= d+
d2 =ln(At/B) + (r − 1
2σ2A)(T − t)
σA√
T − t= d−
(1)
Real-world probabilities from risk-neutral probabilities via µ→ r (WangTransform:)
PDPMerton = N(N−1(PDQMerton)− µA − r
σA
√T
)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 9 / 42
Merton Model PD and LGD
BMertont,T = Be−r(T−t)N (d2) + AtN (−d1)
PDMerton = Pt [AT < B] = N (−d2)
LGDMerton =1
BEt [B − AT |AT < B] = 1− er(T−t) At
B
N (−d1)
N (−d2)
d1 =ln(At/B) + (r + 1
2σ2A)(T − t)
σA√
T − t= d+
d2 =ln(At/B) + (r − 1
2σ2A)(T − t)
σA√
T − t= d−
(1)
Real-world probabilities from risk-neutral probabilities via µ→ r (WangTransform:)
PDPMerton = N(N−1(PDQMerton)− µA − r
σA
√T
)Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 9 / 42
Merton Model Credit Spread
The yield-to-maturity credit spread Y (t,T ) is defined as the spreadover the risk free rate r which prices the bond:
Bt = Be−(r+Y (t,T ))(T−t)
Solving for Y yields
Y (t,T ) =1
T − tln
(B
Bt
)− r
For the Merton Model:
YMerton(t,T ) = − 1
T − tln
[N (d2) +
At
Ber(T−t)N (−d1)
]
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 10 / 42
Merton Model Credit Spread
The yield-to-maturity credit spread Y (t,T ) is defined as the spreadover the risk free rate r which prices the bond:
Bt = Be−(r+Y (t,T ))(T−t)
Solving for Y yields
Y (t,T ) =1
T − tln
(B
Bt
)− r
For the Merton Model:
YMerton(t,T ) = − 1
T − tln
[N (d2) +
At
Ber(T−t)N (−d1)
]
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 10 / 42
Merton Model Credit Spread
The yield-to-maturity credit spread Y (t,T ) is defined as the spreadover the risk free rate r which prices the bond:
Bt = Be−(r+Y (t,T ))(T−t)
Solving for Y yields
Y (t,T ) =1
T − tln
(B
Bt
)− r
For the Merton Model:
YMerton(t,T ) = − 1
T − tln
[N (d2) +
At
Ber(T−t)N (−d1)
]
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 10 / 42
Merton Model Credit Spread
The yield-to-maturity credit spread Y (t,T ) is defined as the spreadover the risk free rate r which prices the bond:
Bt = Be−(r+Y (t,T ))(T−t)
Solving for Y yields
Y (t,T ) =1
T − tln
(B
Bt
)− r
For the Merton Model:
YMerton(t,T ) = − 1
T − tln
[N (d2) +
At
Ber(T−t)N (−d1)
]
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 10 / 42
Merton Model Credit Spread
The yield-to-maturity credit spread Y (t,T ) is defined as the spreadover the risk free rate r which prices the bond:
Bt = Be−(r+Y (t,T ))(T−t)
Solving for Y yields
Y (t,T ) =1
T − tln
(B
Bt
)− r
For the Merton Model:
YMerton(t,T ) = − 1
T − tln
[N (d2) +
At
Ber(T−t)N (−d1)
]
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 10 / 42
Merton Model Parameter Estimation
To compute the desired quantities, model asks for A and σA as inputs.
These are unobservable from the markets.
The solution is to imply them from the market.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 11 / 42
Merton Model Parameter Estimation
To compute the desired quantities, model asks for A and σA as inputs.
These are unobservable from the markets.
The solution is to imply them from the market.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 11 / 42
Merton Model Parameter Estimation
To compute the desired quantities, model asks for A and σA as inputs.
These are unobservable from the markets.
The solution is to imply them from the market.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 11 / 42
Merton Model Parameter Estimation
To compute the desired quantities, model asks for A and σA as inputs.
These are unobservable from the markets.
The solution is to imply them from the market.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 11 / 42
Merton Model Parameter Estimation
There are many ways to do this, but one is to solve the equations
Emarkett = EMerton
t = AtN (d1)− Be−r(T−t)N (d2)
σmarketE Emarket
t = σAAtN (d1).(2)
Note that these equations above are obtained via
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]σVσA
=
∣∣∣∣∣ A∂V∂A
V (A, t)
∣∣∣∣∣ .
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 12 / 42
Merton Model Parameter Estimation
There are many ways to do this, but one is to solve the equations
Emarkett = EMerton
t = AtN (d1)− Be−r(T−t)N (d2)
σmarketE Emarket
t = σAAtN (d1).(2)
Note that these equations above are obtained via
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]σVσA
=
∣∣∣∣∣ A∂V∂A
V (A, t)
∣∣∣∣∣ .
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 12 / 42
Merton Model Parameter Estimation
There are many ways to do this, but one is to solve the equations
Emarkett = EMerton
t = AtN (d1)− Be−r(T−t)N (d2)
σmarketE Emarket
t = σAAtN (d1).(2)
Note that these equations above are obtained via
Et = V (A, t) = E[e−r(T−t)(AT − B)+ | At = A
]σVσA
=
∣∣∣∣∣ A∂V∂A
V (A, t)
∣∣∣∣∣ .
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 12 / 42
Merton Model Criticisms
The assumption that the firm can only default at debt maturity isempirically violated.
Model tends to underestimate default probabilities and credit spreads,especially for short maturities. Indeed
limT→t+
1
T − tPt [AT ≤ B] = 0
Does not take into account empirical evidence that recovery iscorrelated to probability of default.
Does not take into account liquidity issues.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 13 / 42
Merton Model Criticisms
The assumption that the firm can only default at debt maturity isempirically violated.
Model tends to underestimate default probabilities and credit spreads,especially for short maturities. Indeed
limT→t+
1
T − tPt [AT ≤ B] = 0
Does not take into account empirical evidence that recovery iscorrelated to probability of default.
Does not take into account liquidity issues.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 13 / 42
Merton Model Criticisms
The assumption that the firm can only default at debt maturity isempirically violated.
Model tends to underestimate default probabilities and credit spreads,especially for short maturities. Indeed
limT→t+
1
T − tPt [AT ≤ B] = 0
Does not take into account empirical evidence that recovery iscorrelated to probability of default.
Does not take into account liquidity issues.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 13 / 42
Merton Model Criticisms
The assumption that the firm can only default at debt maturity isempirically violated.
Model tends to underestimate default probabilities and credit spreads,especially for short maturities. Indeed
limT→t+
1
T − tPt [AT ≤ B] = 0
Does not take into account empirical evidence that recovery iscorrelated to probability of default.
Does not take into account liquidity issues.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 13 / 42
Merton Model Criticisms
The assumption that the firm can only default at debt maturity isempirically violated.
Model tends to underestimate default probabilities and credit spreads,especially for short maturities. Indeed
limT→t+
1
T − tPt [AT ≤ B] = 0
Does not take into account empirical evidence that recovery iscorrelated to probability of default.
Does not take into account liquidity issues.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 13 / 42
Black-Cox Model Setup
Same asset dynamics as in Merton model:
dAt = µAAtdt + σAAtdW At
Default can happen at times other than maturity, in particular whenthe assets fall below a prescribed default point DP:
τBlack−Cox = mininft ≥ 0 : At ≤ DP, τMerton
In the original Black-Cox paper, DP was taken to beDP = Ce−γ(T−t).
The payoff to the bondholder is
payoffBlack−Cox = Aτ1τ≤T + B1τ>T
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 14 / 42
Black-Cox Model Setup
Same asset dynamics as in Merton model:
dAt = µAAtdt + σAAtdW At
Default can happen at times other than maturity, in particular whenthe assets fall below a prescribed default point DP:
τBlack−Cox = mininft ≥ 0 : At ≤ DP, τMerton
In the original Black-Cox paper, DP was taken to beDP = Ce−γ(T−t).
The payoff to the bondholder is
payoffBlack−Cox = Aτ1τ≤T + B1τ>T
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 14 / 42
Black-Cox Model Setup
Same asset dynamics as in Merton model:
dAt = µAAtdt + σAAtdW At
Default can happen at times other than maturity, in particular whenthe assets fall below a prescribed default point DP:
τBlack−Cox = mininft ≥ 0 : At ≤ DP, τMerton
In the original Black-Cox paper, DP was taken to beDP = Ce−γ(T−t).
The payoff to the bondholder is
payoffBlack−Cox = Aτ1τ≤T + B1τ>T
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 14 / 42
Black-Cox Model Setup
Same asset dynamics as in Merton model:
dAt = µAAtdt + σAAtdW At
Default can happen at times other than maturity, in particular whenthe assets fall below a prescribed default point DP:
τBlack−Cox = mininft ≥ 0 : At ≤ DP, τMerton
In the original Black-Cox paper, DP was taken to beDP = Ce−γ(T−t).
The payoff to the bondholder is
payoffBlack−Cox = Aτ1τ≤T + B1τ>T
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 14 / 42
Black-Cox Model Setup
Same asset dynamics as in Merton model:
dAt = µAAtdt + σAAtdW At
Default can happen at times other than maturity, in particular whenthe assets fall below a prescribed default point DP:
τBlack−Cox = mininft ≥ 0 : At ≤ DP, τMerton
In the original Black-Cox paper, DP was taken to beDP = Ce−γ(T−t).
The payoff to the bondholder is
payoffBlack−Cox = Aτ1τ≤T + B1τ>T
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 14 / 42
Black-Cox Model Setup
Same asset dynamics as in Merton model:
dAt = µAAtdt + σAAtdW At
Default can happen at times other than maturity, in particular whenthe assets fall below a prescribed default point DP:
τBlack−Cox = mininft ≥ 0 : At ≤ DP, τMerton
In the original Black-Cox paper, DP was taken to beDP = Ce−γ(T−t).
The payoff to the bondholder is
payoffBlack−Cox = Aτ1τ≤T + B1τ>T
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 14 / 42
Black-Cox Model Setup
Same asset dynamics as in Merton model:
dAt = µAAtdt + σAAtdW At
Default can happen at times other than maturity, in particular whenthe assets fall below a prescribed default point DP:
τBlack−Cox = mininft ≥ 0 : At ≤ DP, τMerton
In the original Black-Cox paper, DP was taken to beDP = Ce−γ(T−t).
The payoff to the bondholder is
payoffBlack−Cox = Aτ1τ≤T + B1τ>T
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 14 / 42
KMV Model Setup
Moody’s starts by defining a “distance-to-default” DD:
DD =ln A
DP + (µA − σ2A/2)(T − t)
σA√
T − t
which is just d2 in the Merton model with B replaced with DP and rreplaced with µA.
Default point DP chosen as the short term debt plus half oflong-term debt:
DP = ST +1
2LT
Then calibrate DD to empirical distribution Ψ of realized defaultsfrom proprietary database:
PDMoody′s = Ψ(−DD)
Compared to Merton’s estimate of PD (i.e. PDMerton = N (−d2))prediction power is far superior.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 15 / 42
KMV Model Setup
Moody’s starts by defining a “distance-to-default” DD:
DD =ln A
DP + (µA − σ2A/2)(T − t)
σA√
T − t
which is just d2 in the Merton model with B replaced with DP and rreplaced with µA.
Default point DP chosen as the short term debt plus half oflong-term debt:
DP = ST +1
2LT
Then calibrate DD to empirical distribution Ψ of realized defaultsfrom proprietary database:
PDMoody′s = Ψ(−DD)
Compared to Merton’s estimate of PD (i.e. PDMerton = N (−d2))prediction power is far superior.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 15 / 42
KMV Model Setup
Moody’s starts by defining a “distance-to-default” DD:
DD =ln A
DP + (µA − σ2A/2)(T − t)
σA√
T − t
which is just d2 in the Merton model with B replaced with DP and rreplaced with µA.
Default point DP chosen as the short term debt plus half oflong-term debt:
DP = ST +1
2LT
Then calibrate DD to empirical distribution Ψ of realized defaultsfrom proprietary database:
PDMoody′s = Ψ(−DD)
Compared to Merton’s estimate of PD (i.e. PDMerton = N (−d2))prediction power is far superior.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 15 / 42
KMV Model Setup
Moody’s starts by defining a “distance-to-default” DD:
DD =ln A
DP + (µA − σ2A/2)(T − t)
σA√
T − t
which is just d2 in the Merton model with B replaced with DP and rreplaced with µA.
Default point DP chosen as the short term debt plus half oflong-term debt:
DP = ST +1
2LT
Then calibrate DD to empirical distribution Ψ of realized defaultsfrom proprietary database:
PDMoody′s = Ψ(−DD)
Compared to Merton’s estimate of PD (i.e. PDMerton = N (−d2))prediction power is far superior.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 15 / 42
KMV Model Setup
Moody’s starts by defining a “distance-to-default” DD:
DD =ln A
DP + (µA − σ2A/2)(T − t)
σA√
T − t
which is just d2 in the Merton model with B replaced with DP and rreplaced with µA.
Default point DP chosen as the short term debt plus half oflong-term debt:
DP = ST +1
2LT
Then calibrate DD to empirical distribution Ψ of realized defaultsfrom proprietary database:
PDMoody′s = Ψ(−DD)
Compared to Merton’s estimate of PD (i.e. PDMerton = N (−d2))prediction power is far superior.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 15 / 42
American Airlines Default
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 16 / 42
MF Global Default
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 17 / 42
Bond Price under Correlated A-R Model
We assume
Existence of a risk-neutral measure P with risk-free rate rf .
Default τ is adapted to the filtration Ft = σ(At ,Rt).
A recovery process Rt .
Bond has maturity T .
It follows that
Bt(ω) = Be−rf (T−t)Pt [τ > T ] + Et
[e−rf (T−t)RT1τ=T
]+ Et
[e−rf (τ−t)Rτ1τ<T
].
(3)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 18 / 42
Complete Recovery Upon Default and No Default
If it happens that the entire arbitrage-free value of the bond is recoveredupon default, i.e. under risk-free rate rf and risk-neutral measure P,
Et [Rs ] = Be−rf (T−s) (4)
then the entire no-default value is retained:
Bt(ω) = Be−rf (T−t)Pt [τ > T ] + Et
[e−rf (T−t)B1τ=T
]+
∫ T
te−rf (s−t)Be−rf (T−s)Pt [τ ∈ ds]
= Be−rf (T−t)
(5)
Of course, if Pt [τ > T ] = 1, then Pt [τ ∈ ds] = 0 for all s ∈ [t,T ] and soBt = Be−rf (T−t) once again.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 19 / 42
Example-Basic Hazard Rate Model
As an initial example to motivate bond pricing formula, assume that bothdefault time and recovery are independent of the Asset filtration, anddefault time is in fact memoryless:
Pt [τ > u] = e−λ(u−t) for some λ > 0 and all u ≥ t ≥ 0.
Et [e−rf sRs ] = e−rf tRt .
It follows that
Bt(ω) = Be−rf (T−t)e−λ(T−t) + Rt(ω) · (1− e−λ(T−t)) and
Y (t,T )(ω) = − 1T−t ln
[e−λ(T−t) + Rt(ω)
Be−rf (T−t) (1− e−λ(T−t))]
limT→t+ Y (t,T )(ω) = λ(
1− Rt(ω)
B
).
Note that the short term credit spread is positive a.e. as long asPt
[Rt < B
]= 1.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 20 / 42
Bond Price under Correlated A-R Model
Define the quantities:
At , the asset value at time t > 0
Rt , the recovery amount at time t > 0. We model recovery as a”shadow” asset, and thus follows the same dynamics as the asset.
The dynamics for the asset and recovery are, under a risk neutral measureP,
dAt
At= rf dt + σAdW A
t
dRt
Rt= rf dt + σRdW R
t .
(6)
The risk drivers are correlated via
E[dW At dW R
t ] = ρA,Rdt. (7)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 21 / 42
Bond Price under Correlated A-R Model
Define the quantities:
At , the asset value at time t > 0
Rt , the recovery amount at time t > 0. We model recovery as a”shadow” asset, and thus follows the same dynamics as the asset.
The dynamics for the asset and recovery are, under a risk neutral measureP,
dAt
At= rf dt + σAdW A
t
dRt
Rt= rf dt + σRdW R
t .
(6)
The risk drivers are correlated via
E[dW At dW R
t ] = ρA,Rdt. (7)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 21 / 42
Bond Price under Correlated A-R Model
Define the quantities:
At , the asset value at time t > 0
Rt , the recovery amount at time t > 0. We model recovery as a”shadow” asset, and thus follows the same dynamics as the asset.
The dynamics for the asset and recovery are, under a risk neutral measureP,
dAt
At= rf dt + σAdW A
t
dRt
Rt= rf dt + σRdW R
t .
(6)
The risk drivers are correlated via
E[dW At dW R
t ] = ρA,Rdt. (7)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 21 / 42
Two Factor Merton Model - Default at Maturity
If we allow for a shadow recovery process as in equation (6), then we areleft with an exchange option where the payoff at expiry is
G (AT ,RT ) = RT1AT<B + B1AT≥B. (8)
Define
Default =
AT ≥ Bc
α := δ +1
2σ2R(1− ρ2
A,R) + γ(
rf −1
2σ2A
)+γ2σ2
A
2
γ := ρA,RσRσA
δ := (rf −1
2σ2R)− γ(rf −
1
2σ2A).
(9)
Note that ρA,R = γ = 1 implies that δ = 0 and α = rf .
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 22 / 42
Two Factor Merton Model - Default at Maturity
Consequently,
Bt = e−rf (T−t)Et
[RT1AT<B + B1AT≥B
]= Et
[e−rf (T−t)RT1AT<B
]+ Be−rf (T−t) · Pt [AT ≥ B]
= Rte(α−rf )(T−t)Φ
(ln B
At− (rf − 1
2σ2A)(T − t)− γσ2
A(T − t)
σA√
T − t
)
+ Be−rf (T−t) ·
(1− Φ
(ln B
At− (rf − 1
2σ2A)(T − t)
σA√
T − t
))(10)
Note that we retain the classical 1d Merton price if ρA,R = γ = 1.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 23 / 42
Two Factor Merton Model - Default at Maturity
Recovery metrics:
Et [Loss | Default] =Et [B − RT | AT < B]
B
= 1− Rt
Be−α(T−t)
Φ
(ln B
At−(rf− 1
2σ2A)(T−t)−γσ2
A(T−t)
σA√T−t
)
Φ
(ln B
At−(rf− 1
2σ2A)(T−t)
σA√T−t
)
Pt [Default] = Φ
(ln B
At− (rf − 1
2σ2A)(T − t)
σA√
T − t
)
Y2D Merton(t,T ) =1
T − tln
(1
1− Pt [Default]Et [Loss | Default]
)
(11)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 24 / 42
Consistency: 2d vs 1d Merton
Finally, it should be noted that since
limγ→1
dγ = d1
limρ→1,γ→1
α = rf
limρ→1,γ→1,R0→A0
P[At = Rt ] = 1,
(12)
it follows that
limρ→1,γ→1,Rt→At
Y2d Merton(t,T ) = YMerton(t,T ). (13)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 25 / 42
Two Factor Black-Cox Model - Stopping Times
Let DP define our default point written into the bondholder covenant onthe asset A, and define τDP as the first time A reaches this default point.
Furthermore, define 2dBC default time τ as
τ =
τDP : τDP < TT : τDP ≥ T ∩
AT < B
∞ : otherwise.
Equivalently,
Default =τDP > T ,AT ≥ B
c. (14)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 26 / 42
Two Factor Black-Cox Model - Stopping Times
Let DP define our default point written into the bondholder covenant onthe asset A, and define τDP as the first time A reaches this default point.
Furthermore, define 2dBC default time τ as
τ =
τDP : τDP < TT : τDP ≥ T ∩
AT < B
∞ : otherwise.
Equivalently,
Default =τDP > T ,AT ≥ B
c. (14)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 26 / 42
Weak Covenant Model: DP < B
Theorem
B2d Black Coxt,T = Be−rf (T−t) · Pt [AT ≥ B, τDP > T ]
+[Rt − Et [e
−rf (T−t)RT1AT≥B,τDP>T]]
:= Be−rf (T−t)[1− u(w , y ,T − t)
]+ v(Rt ,w , y ,T − t)
y = lnDP
At≤ 0
w = lnB
At≤ 0
µ = rf −1
2σ2A
γ = ρA,RσRσA.
(15)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 27 / 42
Weak Covenant Model: DP < B
u(w , y ,T − t) = N
w − µ(T − t)√σ2A(T − t)
+ e
2µy
σ2A N
−w − 2y − µ(T − t)√σ2A(T − t)
v(Rt ,w , y ,T − t) = RtN
w − (µ+ γσ2A)(T − t)√
σ2A(T − t)
+ Rte
2γy+ 2µy
σ2A N
−w − 2y − (µ+ γσ2A)(T − t)√
σ2A(T − t)
.
(16)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 28 / 42
Weak Covenant Model Price - Sketch of Proof
We can also complete this calculation using the fact that e−rf tRt is a localmartingale, and so for the bounded stopping time τ := min τDP ,T,
e−rf tRt = Et [e−rf τRτ ] = Et [e
−rf τRτ1τ≤T] + Et [e−rf τRτ1τ>T]
= Et [e−rf τDP RτDP
1τDP≤T] + Et [e−rf TRT1τDP>T]
(17)
It follows that
Bt = Rt + Be−rf (T−t) · Pt [AT ≥ B, τDP > T ]
− Rt
Aγte−(rf−δ− 1
2σ2R(1−ρ2
A,R))(T−t) ·∫ ∞DP
aγPt
[AT ∈ da, τDP > T
](18)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 29 / 42
Weak Covenant Model Price - Sketch of Proof
We calculate the remaining integral using the identities from the DoubleLookbacks paper. We begin with a standard Brownian motion W on aprobability space and define
Xt = µt + σWt
τa = min t : Xt = aX t = min
0≤s≤tXs
g(x , y , t, µ) :=1
σ√
tφ(x − µt
σ√
t
)(1− exp
(4y 2 − 4xy
2σ2t
)) (19)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 30 / 42
Weak Covenant Model Price - Sketch of Proof
The authors of the Double Lookback paper prove that
P [Xt ∈ dx ,X t ≥ y ] = g(−x ,−y , t,−µ)dx
=1
σ√
tφ(−x + µt
σ√
t
)(1− exp
(4y 2 − 4xy
2σ2t
))
=1
σ√
tφ(− (x − µt)
σ√
t
)(1− exp
(− 4y(x − y)
2σ2t
))(20)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 31 / 42
Weak Covenant Model Price - Sketch of Proof
By setting
µ := rf −1
2σ2A
σ := σA
(21)
it follows that
Xt = lnAt
A0
X t = min0≤s≤t
lnAs
A0
(22)
and so for y = ln DPA0
,
At = A0eXt
τDP > T =
XT > ln
(DP
A0
)=τXy > T
.
(23)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 32 / 42
Weak Covenant Model Price - Sketch of Proof
Using this notation, we combine the above to retain,
∫ ∞DP
aγ · Pt
[AT ∈ da, τDP > T
]= Et
[AγT1τDP>T
]
= E0
[eγ
(ln (At)+XT−t
)1τXy >T−t
]
=
∫ ∞y
eγ(x+lnAt)P0
[XT−t ∈ dx , τXy > T − t
]
= (At)γ
∫ ∞y
1√2πσ2
A(T − t)e
(− (x−µ(T−t))2−2σ2
Aγ(T−t)
2σ2A
(T−t)
)dx
− (At)γ
∫ ∞y
1√2πσ2
A(T − t)e
(− (x−µ(T−t))2+4y(x−y)−2σ2
Aγ(T−t)
2σ2A
(T−t)
)dx .
(24)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 33 / 42
Consistency: Reduction to 1-D Black-Cox Model
As a result of the closed form above for Bt,T , the consistency of the modelas T → t follows quickly:
Lemma
limT→t+ B2d Black Coxt,T = B.
Proof.
Without loss of generality, we assume t = 0. As y ,w < 0,
limT→0+
[N
−w − µT√σ2AT
− e2µy
σ2A N
−w − 2y − µT√σ2AT
] = 1
limT→0+
[N
w − (µ+ γσ2A)T√
σ2AT
+ e2γy+ 2µy
σ2A N
−w − 2y − (µ+ γσ2A)T√
σ2AT
]
= 0.(25)
and our result follows.
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 34 / 42
Consistency: Reduction to 1-D Black-Cox Model
B1d Black Coxt,T = lim
(Rt ,ρA,R ,σR)→(At ,1,σA)B2d Black Coxt,T
= Be−rf (T−t)N
− ln BAt− µ−(T − t)√σ2A(T − t)
− Be−rf (T−t)
(DP
At
) 2µ−
σ2A N
− ln BAtDP2 − µ−(T − t)√
σ2A(T − t)
+ At
[N
ln BAt− µ+(T − t)√σ2A(T − t)
+(DP
At
) 2µ+
σ2A N
− ln BAtDP2 − µ+(T − t)√
σ2A(T − t)
].µ+ = rf +
1
2σ2A
µ− = rf −1
2σ2A.
(26)Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 35 / 42
Credit Spread: 2-D Black-Cox Model
By appealing to the martingale nature of recovery, and Bayes’ Theorem,
Y2dBC (t,T ) =1
T − tln
(1
1− Et [Loss | Default] · Pt [Default]
)Et [Loss | Default] = Et
[ B − RT
B| Default
]= 1− Et [e
−rf (T−t)RT | Default]
Be−rf (T−t)
= 1−Rt − Et [e
−rf (T−t)RT1 No Default]
Be−rf (T−t)Pt [Default]
= 1− v(Rt ,w , y ,T − t)
Be−rf (T−t)[1− u(w , y ,T − t)]
Pt [Default] = 1− u(w , y ,T − t) = PD1dBCt,T .
(27)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 36 / 42
CDS: 2-D Black-Cox Model
Without loss of generality, we can define the CDS Premium at time 0.Under the usual (EPP) framework for continuous payment, premium rateP0,T
=E0[e−rf τDP (B − RτDP
)1τDP≤T] + E0[e−rf T (B − RT )1AT<B,τDP>T]∫ T0 e−rf s P0[τDP > s]ds
=E0[e−rf τDP B1τDP≤T] + E0[e−rf T B1AT<B,τDP>T]− v(R0,w , y ,T )∫ T
0 e−rf s P0[τDP > s]ds
=B(E0[e−rf τDP 1τDP≤T] + e−rf T P0[AT < B, τDP > T ]
)− v(R0,w , y ,T )∫ T
0 e−rf s P0[τDP > s]ds(28)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 37 / 42
CDS: 2-D Black-Cox Model
It follows that
P0,T =B(h(A0,T ) + e−rf T [F (T )− u(w , y ,T )]
)− v(R0,w , y ,T )∫ T
0 e−rf sF (s)ds
= rfB(h(A0,T ) + e−rf T [F (T )− u(w , y ,T )]
)− v(R0,w , y ,T )
1− e−rf TF (T )− h(A0,T )
F (s) = N
−w + µs√σ2As
− e2µy
σ2A N
−w + 2y + µs√σ2As
h(A0,T ) = E0[e−rf τDP 1τDP≤T]
=A0
[N( ln B
A0−(rf + 1
2σ2A)T√
σ2AT
)−(DPA0
) 2(rf + 12σ
2A)
σ2A N
(2 ln DPA0−ln B
A0+(rf + 1
2σ2A)T√
σ2AT
)]DP
.
(29)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 38 / 42
CDS: 2-D Black-Cox Model
It follows that
P0,T =B(h(A0,T ) + e−rf T [F (T )− u(w , y ,T )]
)− v(R0,w , y ,T )∫ T
0 e−rf sF (s)ds
= rfB(h(A0,T ) + e−rf T [F (T )− u(w , y ,T )]
)− v(R0,w , y ,T )
1− e−rf TF (T )− h(A0,T )
F (s) = N
−w + µs√σ2As
− e2µy
σ2A N
−w + 2y + µs√σ2As
h(A0,T ) = E0[e−rf τDP 1τDP≤T]
=A0
[N( ln B
A0−(rf + 1
2σ2A)T√
σ2AT
)−(DPA0
) 2(rf + 12σ
2A)
σ2A N
(2 ln DPA0−ln B
A0+(rf + 1
2σ2A)T√
σ2AT
)]DP
.
(29)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 38 / 42
Conclusions and Next Papers?
Have extended 2d models to include clsoed form solutions (bothMerton and Black-Cox)
Recovery is unbounded. Historically possible (foreclosure and bankfees.)
Can include bounded recovery in this framework, work underway.
Can extend to other products, such as Credit Linked Notes.
Calibration to market data for both CDS and Bond prices (anytakers?)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 39 / 42
Acknowledgements
Gary Parker (SFU)
Yang Wang (MSU)
Keith Promislow (MSU)
Emil Valdez (MSU)
Steven Shreve (CMU)
Dmitry Kramkov (CMU)
Joe Campolieti (WLU)
Peter Carr (Morgan Stanley)
All Of You!!
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 40 / 42
References
V.V. Acharya, T.S. Bharath, & A. Srinivasan, Does industry-widedistress affect defaulted firms? Evidence from creditor recoveries,Journal of Financial Economics 85 (2007) 787-821.E.I. Altman, B. Brady, A. Resti, & A. Sironi, The Link BetweenDefault and Recovery Rates: Theory, Empirical Evidence andImplications, The Journal of Business ,Vol. 78, No. 6, November2005.Black, F., & Cox, J.C., Valuing Corporate Securities: Some Effects
of Bond Indenture Provisions, Journal of Finance 31, 1976, 351-367.Levy, A. and Hu, A., Incorporating Systematic Risk in Recovery:Theory and Evidence, Modeling Methodology, Moody’s KMV, 2007.G. Giese, The Impact of PD/LGD Correlations on Credit RiskCapital, Risk, April 2005, pp 79-85.He, H, Keirstead, W.P., and Rebholz, J., Double Lookbacks,Mathematical Finance, Vol. 8, No 3 1998 (201-228).Merton, R., On the Pricing of Corporate Debt: the Risk Structure ofInterest Rates, Journal of Finance 29, 1974, 449-470.Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 41 / 42
Where it all started!! Albert and Nick (circa 1999)
Albert Cohen (MSU) Bond and CDS Pricing with Stochastic Recovery : Moody’s PD-LGD Correlation ModelSimon Fraser University 42 / 42