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Challenges in xVA Pricing and Risk
Andrew McClelland, PhDDirector of Quantitative Research
Numerix
Matlab Computational Finance ConferenceNYC 2017
September 28, 2017
Andrew McClelland, Numerix xVA Pricing and Risk 1/13
Presentation Outline
Quick overview of Numerix and why we prioritize xVA
What is xVA? Some intuition for how things come together
Computational di�culties encountered in xVA
Multi-factor hybrid models and American Monte Carlo1
Matlab for complicated exposures modeling and aggregations
1Used when referring to Least-Squares Monte Carlo, a la Longsta� andSchwartz ('01), in the context of exposures calculations.
Andrew McClelland, Numerix xVA Pricing and Risk 2/13
Numerix Overview 1
Numerix2 founded in '96, headquartered in NYC, 250+ employees
It has origins as a pricing & risk library for derivatives
Oriented towards exotic & multi-factor derivatives, eg . PRDCs
Managing risk for exotics is a very complicated process
Requires sophisticated & delicate models, methods, calibrations etc .
2https://www.numerix.com.Andrew McClelland, Numerix xVA Pricing and Risk 3/13
Numerix Overview 1
Numerix3 founded in '96, headquartered in NYC, 250+ employees
It has origins as a pricing & risk library for derivatives
Oriented towards exotic & multi-factor derivatives, eg . PRDCs
Managing risk for exotics is a very complicated process
Requires sophisticated & delicate models, methods, calibrations etc .
3https://www.numerix.com.Andrew McClelland, Numerix xVA Pricing and Risk 3/13
Pricing Work�ow
Market Data
Calibrated Model
ExoticValuation
rate curves
vol surfaces
FX levels
forward rates
short rate factors
local/stochastic vol
Monte Carlo
PDE
lattice/tree
Figure: Standard pricing work�ow. First, market data such as volatility surfaces are
sourced, transformed and cleansed. Second, a pricing model is calibrated to the market
data. Third, a pricing method such as Monte Carlo is invoked to compute the price.
Andrew McClelland, Numerix xVA Pricing and Risk 3/13
Risk Work�ow
Market Data
Calibrated Model
ExoticValuation
MarketData'
CalibratedModel'
ExoticValuation'
rate curves
vol surfaces
FX levels
forward rates
short rate factors
local/stochastic vol
Monte Carlo
PDE
lattice/tree
Figure: Standard risk work�ow. Risk factors among market data and model elements,
eg . yield nodes and model parameters, are identi�ed as risk factors. Sensitivities against
these factors are computed and are hedged using vanilla instruments.
Andrew McClelland, Numerix xVA Pricing and Risk 3/13
Risk Work�ow
Market Data
Calibrated Model
ExoticValuation
MarketData'
CalibratedModel'
ExoticValuation'
rate curves
vol surfaces
FX levels
forward rates
short rate factors
local/stochastic vol
Monte Carlo
PDE
lattice/tree
HedgeValuation
HedgeValuation'
Figure: Standard risk work�ow. Risk factors among market data and model elements,
eg . yield nodes and model parameters, are identi�ed as risk factors. Sensitivities against
these factors are computed and are hedged using vanilla instruments.
Andrew McClelland, Numerix xVA Pricing and Risk 3/13
Risk Work�ow
Market Data
Calibrated Model
ExoticValuation
MarketData'
CalibratedModel'
ExoticValuation'
rate curves
vol surfaces
FX levels
forward rates
short rate factors
local/stochastic vol
Monte Carlo
PDE
lattice/tree
HedgeValuation
HedgeValuation'
Figure: Standard risk work�ow. Risk factors among market data and model elements,
eg . yield nodes and model parameters, are identi�ed as risk factors. Sensitivities against
these factors are computed and are hedged using vanilla instruments.
Andrew McClelland, Numerix xVA Pricing and Risk 3/13
Numerix Overview 2
After crisis exotics volumes dropped but xVAs, eg . CVA, emerged
Big challenge for banks and managing xVA resembles managing exotics
Nice use case for how our clients use a mix of NX and Matlab
Content should be interesting for this audience also
Sits within larger issue of holistic modeling of trade impact
Andrew McClelland, Numerix xVA Pricing and Risk 4/13
Numerix Overview 2
After crisis exotics volumes dropped but xVAs, eg . CVA, emerged
Big challenge for banks and managing xVA resembles managing exotics
Nice use case for how our clients use a mix of NX and Matlab
Content should be interesting for this audience also
Sits within larger issue of holistic modeling of trade impact
Andrew McClelland, Numerix xVA Pricing and Risk 4/13
Numerix Matlab Interface
Figure: Example of a CVA calculation using the Matlab interface for NX in combination
with native Matlab functionality.
Andrew McClelland, Numerix xVA Pricing and Risk 4/13
Numerix Overview 2
After crisis exotics volumes dropped but xVAs, eg . CVA, emerged
Big challenge for banks and managing xVA resembles managing exotics
Nice use case for how our clients use a mix of NX and Matlab
Content should be interesting for this audience also
Sits within larger issue of holistic modeling of trade impact
Andrew McClelland, Numerix xVA Pricing and Risk 4/13
Numerix Overview 2
After crisis exotics volumes dropped but xVAs, eg . CVA, emerged
Big challenge for banks and managing xVA resembles managing exotics
Nice use case for how our clients use a mix of NX and Matlab
Content should be interesting for this audience also
Sits within larger issue of holistic modeling of trade impact
Andrew McClelland, Numerix xVA Pricing and Risk 4/13
What is xVA?
Traditional valuations involve the risk-neutral valuation formula
Classical Valuation
V (t) = Et
[e−
∫ Tt r(u) duC(T )
]Many ways to derive this formula, equilibrium4, arbitrage5, etc .
Hedging approach6 is a bit restrictive but mimics bank practice
Classical hedging assumptions ignore certain �frictions�
eg . counterparty credit risk, funding spreads & collateral
4eg . Cox, Ingersol and Ross ('85).5eg . Harrison and Kreps ('79).6eg . Black and Scholes ('73) or Burgard and Kjaer ('11).
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
What is xVA?
Traditional valuations involve the risk-neutral valuation formula
Classical Valuation
V (t) = Et
[e−
∫ Tt r(u) duC(T )
]Many ways to derive this formula, equilibrium7, arbitrage8, etc .
Hedging approach9 is a bit restrictive but mimics bank practice
Classical hedging assumptions ignore certain �frictions�
eg . counterparty credit risk, funding spreads & collateral
7eg . Cox, Ingersol and Ross ('85).8eg . Harrison and Kreps ('79).9eg . Black and Scholes ('73) or Burgard and Kjaer ('11).
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
Valuations via Hedging Arguments
Swap HedgeCounterparty
CDS HedgeCounterparty
Bank ClientStructured Swap
Risk-Free Funding Funding Account
Vanilla Swaps
CustodianClearing House
Figure: Basic considerations within hedging derivation of valuation rule.
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
What is xVA?
Traditional valuations involve the risk-neutral valuation formula
Classical Valuation
V (t) = Et
[e−
∫ Tt r(u) duC(T )
]Many ways to derive this formula, equilibrium10, arbitrage11, etc .
Hedging approach12 is a bit restrictive but mimics bank practice
Classical hedging assumptions ignore certain �frictions�
eg . counterparty credit risk, funding spreads & collateral
10eg . Cox, Ingersol and Ross ('85).11eg . Harrison and Kreps ('79).12eg . Black and Scholes ('73) or Burgard and Kjaer ('11).
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
Valuations via Hedging Arguments
Swap HedgeCounterparty
CDS HedgeCounterparty
Bank ClientStructured Swap
Risk-Free Funding Funding Account
Vanilla Swaps
CustodianClearing House
Figure: Modern considerations within hedging derivation of valuation rule, including
counterparty credit risk, funding costs, initial margin requirements.
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
Valuations via Hedging Arguments
Swap HedgeCounterparty
CDS HedgeCounterparty
Bank ClientStructured Swap
Treasury Funding Funding Account
Vanilla Swaps
CustodianClearing House
Figure: Modern considerations within hedging derivation of valuation rule, including
counterparty credit risk, funding costs, initial margin requirements.
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
Valuations via Hedging Arguments
Swap HedgeCounterparty
CDS HedgeCounterparty
Bank ClientStructured Swap
Treasury Funding Funding Account
Vanilla Swaps
CDS Contracts
CustodianClearing House
Figure: Modern considerations within hedging derivation of valuation rule, including
counterparty credit risk, funding costs, initial margin requirements.
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
Valuations via Hedging Arguments
Swap HedgeCounterparty
CDS HedgeCounterparty
Bank ClientStructured Swap
Treasury Funding Funding Account
Vanilla Swaps
CDS Contracts
CustodianClearing House
Initia
l Marg
in
Figure: Modern considerations within hedging derivation of valuation rule, including
counterparty credit risk, funding costs, initial margin requirements.
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
Valuations via Hedging Arguments
Swap HedgeCounterparty
CDS HedgeCounterparty
Bank ClientStructured Swap
Treasury Funding Funding Account
Vanilla Swaps
CDS Contracts
CustodianClearing House
Initia
l Marg
in
Figure: Modern considerations within hedging derivation of valuation rule, including
counterparty credit risk, funding costs, initial margin requirements.
Andrew McClelland, Numerix xVA Pricing and Risk 5/13
What is CVA?
Counterparty credit risk =⇒ �credit valuation adjustment"13 or CVA
Basically upfront cost of dynamically hedging counterparty default
Must be added to classical value, or cooked into deal payments
Credit Valuation Adjustment
CVA(t) = Et
[Lifetime Discounted Counterparty Loss(t,T )
]IFRS13 (accounting standard) requires CVA be recorded in statements
Basel III extended capital framework to include a CVA charge
13eg . Du�e and Canabarro ('04) and Gregory ('15).Andrew McClelland, Numerix xVA Pricing and Risk 6/13
What is CVA?
Counterparty credit risk =⇒ �credit valuation adjustment"14 or CVA
Basically upfront cost of dynamically hedging counterparty default
Must be added to classical value, or cooked into deal payments
Credit Valuation Adjustment
CVA(t) = Et
[Lifetime Discounted Counterparty Loss(t,T )
]IFRS13 (accounting standard) requires CVA be recorded in statements
Basel III extended capital framework to include a CVA charge
14eg . Du�e and Canabarro ('04) and Gregory ('15).Andrew McClelland, Numerix xVA Pricing and Risk 6/13
What is CVA?
Counterparty credit risk =⇒ �credit valuation adjustment"15 or CVA
Basically upfront cost of dynamically hedging counterparty default
Must be added to classical value, or cooked into deal payments
Credit Valuation Adjustment
CVA(t) = Et
[∫ T
tDiscounted Counterparty Loss(s) ds
]IFRS13 (accounting standard) requires CVA be recorded in statements
Basel III extended capital framework to include a CVA charge
15eg . Du�e and Canabarro ('04) and Gregory ('15).Andrew McClelland, Numerix xVA Pricing and Risk 6/13
What is CVA?
Counterparty credit risk =⇒ �credit valuation adjustment"16 or CVA
Basically upfront cost of dynamically hedging counterparty default
Must be added to classical value, or cooked into deal payments
Credit Valuation Adjustment
CVA(t) = Et
[∫ T
te−
∫ st r(u) duλ(s)(V (s))+ ds
]IFRS13 (accounting standard) requires CVA be recorded in statements
Basel III extended capital framework to include a CVA charge
16eg . Du�e and Canabarro ('04) and Gregory ('15).Andrew McClelland, Numerix xVA Pricing and Risk 6/13
What is CVA?
Counterparty credit risk =⇒ �credit valuation adjustment"17 or CVA
Basically upfront cost of dynamically hedging counterparty default
Must be added to classical value, or cooked into deal payments
Credit Valuation Adjustment
CVA(t) = Et
[∫ T
te−
∫ st r(u) duλ(s)(V (s))+ ds
]IFRS13 (accounting standard) requires CVA be recorded in statements
Basel III extended capital framework to include a CVA charge
17eg . Du�e and Canabarro ('04) and Gregory ('15).Andrew McClelland, Numerix xVA Pricing and Risk 6/13
CVA Complications: Counterparty Aggregation
Crucial to note that CVA is computed at the counterparty level
Assume swaps with values V swap1
and V swap2
with counterparty
Portfolio exposure is not the sum of individual swap exposures
Portfolio Exposure Aggregation
(V pfolio)+ = (V swap1
+ V swap2
)+ 6= (V swap1
)+ + (V swap2
)+
Clearly V swap2
< 0 could o�set V swap1
> 0, and vica versa
Thus the incremental CVA involves whole counterparty portfolio
Why xVA calcs are so expensive... some xVAs involve many c/parties!
Andrew McClelland, Numerix xVA Pricing and Risk 7/13
A Practical CVA Computation
Evaluate the CVA formula via discretization and Monte Carlo
Use p = 1, . . . ,P paths and i = 0, · · · ,T timesteps
CVA Calculation
CVA(t0) =1
P
T∑i=1
P∑p=1
λp(si )e−
∫ sit rp(u) du(Vp(si ))+ ∆si
1 Simulate paths state variables Xp,i , eg . rates, hazards, FX
2 Revalue portfolio along all paths V pfoliop,i = V swap
1,p,i + · · ·
3 Evaluate (Vp,i )+, weight by discount factors & hazards and aggregate
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
A Practical CVA Computation
Evaluate the CVA formula via discretization and Monte Carlo
Use p = 1, . . . ,P paths and i = 0, · · · ,T timesteps
CVA Calculation
CVA(t0) =1
P
T∑i=1
P∑p=1
λp(si )e−
∫ sit rp(u) du(Vp(si ))+ ∆si
1 Simulate paths state variables Xp,i , eg . rates, hazards, FX
2 Revalue portfolio along all paths V pfoliop,i = V swap
1,p,i + · · ·
3 Evaluate (Vp,i )+, weight by discount factors & hazards and aggregate
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
CVA Simulation Steps
0 1 2 3 4 5 6 7 8 9 10
Horizon (Yrs)
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06Short Rate Trajectories
Figure: Example of simulations involved in a CVA calculation. Portfolio consists of a
5Y swap and a 10Y swap.
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
CVA Simulation Steps
0 1 2 3 4 5 6 7 8 9 10
Horizon (Yrs)
-0.3
-0.2
-0.1
0
0.1
0.2
0.310Y Swap Trajectories
Figure: Example of simulations involved in a CVA calculation. Portfolio consists of a
5Y swap and a 10Y swap.
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
CVA Simulation Steps
0 1 2 3 4 5 6 7 8 9 10
Horizon (Yrs)
-0.15
-0.1
-0.05
0
0.05
0.15Y Swap Trajectories
Figure: Example of simulations involved in a CVA calculation. Portfolio consists of a
5Y swap and a 10Y swap.
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
CVA Simulation Steps
0 1 2 3 4 5 6 7 8 9 10
Horizon (Yrs)
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3Portfolio Trajectories
Figure: Example of simulations involved in a CVA calculation. Portfolio consists of a
5Y swap and a 10Y swap.
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
CVA Simulation Steps
0 1 2 3 4 5 6 7 8 9 10
Horizon (Yrs)
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3Positive Portfolio Trajectories
Figure: Example of simulations involved in a CVA calculation. Portfolio consists of a
5Y swap and a 10Y swap.
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
CVA Simulation Steps
0 1 2 3 4 5 6 7 8 9 10
Horizon (Yrs)
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3Positive Portfolio Trajectories
Figure: Example of simulations involved in a CVA calculation. Portfolio consists of a
5Y swap and a 10Y swap.
Andrew McClelland, Numerix xVA Pricing and Risk 8/13
Main Challenges in CVA
Portfolios can span multiple risk factors, eg . swaps in many CCYs
Building models is di�cult and building hybrid models is more so
Require correlation structures for (latent) variables & joint calibration
Computing Vp,i can be an O(P2) problem for exotics
In practice this can be extremely expensive and we try to avoid
American MC (AMC) is a powerful regression-based O(P) algorithm
Andrew McClelland, Numerix xVA Pricing and Risk 9/13
American Monte Carlo
Etymology from its use in pricing American (early-exercise) options
Idea is to use the original P paths to build future values via projection
Future Values by Regression
V (t) = Et [C(T )] =⇒
C(X (T )) = V (X (t)) + ε(t,T ), Et [ε(t,T )] = 0
y = f (x) + υ, E[υ] = 0
Evaluated via regression with f (·) = β0φ0(·) + β1φ1(·) + · · ·
Selection of basis functions φ(·) crucial, especially in high dimensions
Di�cult to implement for generic products with scripted payo�s
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
American Monte Carlo
Etymology from its use in pricing American (early-exercise) options
Idea is to use the original P paths to build future values via projection
Future Values by Regression
V (t) = Et [C(T )] =⇒
C(X (T )) = V (X (t)) + ε(t,T ), Et [ε(t,T )] = 0
y = f (x) + υ, E[υ] = 0
Evaluated via regression with f (·) = β0φ0(·) + β1φ1(·) + · · ·
Selection of basis functions φ(·) crucial, especially in high dimensions
Di�cult to implement for generic products with scripted payo�s
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
American Monte Carlo
Etymology from its use in pricing American (early-exercise) options
Idea is to use the original P paths to build future values via projection
Future Values by Regression
V (t) = Et [C(T )] =⇒
C(Xp(T )) = V (Xp(t)) + εp(t,T ), Et [εp(t,T )] = 0
y = f (x) + υ, E[υ] = 0
Evaluated via regression with f (·) = β0φ0(·) + β1φ1(·) + · · ·
Selection of basis functions φ(·) crucial, especially in high dimensions
Di�cult to implement for generic products with scripted payo�s
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
American Monte Carlo
Etymology from its use in pricing American (early-exercise) options
Idea is to use the original P paths to build future values via projection
Future Values by Regression
V (t) = Et [C(T )] =⇒
C(Xp(T )) = V (Xp(t)) + εp(t,T ), Et [εp(t,T )] = 0
y = f (x) + υ, E[υ] = 0
Evaluated via regression with f (·) = β0φ0(·) + β1φ1(·) + · · ·
Selection of basis functions φ(·) crucial, especially in high dimensions
Di�cult to implement for generic products with scripted payo�s
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
American Monte Carlo
Etymology from its use in pricing American (early-exercise) options
Idea is to use the original P paths to build future values via projection
Future Values by Regression
V (t) = Et [C(T )] =⇒
C(Xp(T )) = V (Xp(t)) + εp(t,T ), Et [εp(t,T )] = 0
yp = f (xp) + υp, E[υp] = 0
Evaluated via regression with f (·) = β0φ0(·) + β1φ1(·) + · · ·
Selection of basis functions φ(·) crucial, especially in high dimensions
Di�cult to implement for generic products with scripted payo�s
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
American Monte Carlo Example
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12
Short Rate(t)
0
0.05
0.1
0.15
0.2
0.25American MC for a Bermudan
Cashflow(T)Value(t)
Figure: Example of AMC for a simple Bermudan swaption. Pathwise cash�ows are
projected onto the short rate using a Hull White ('90) model.
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
American Monte Carlo
Etymology from its use in pricing American (early-exercise) options
Idea is to use the original P paths to build future values via projection
Future Values by Regression
V (t) = Et [C(T )] =⇒
C(Xp(T )) = V (Xp(t)) + εp(t,T ), Et [εp(t,T )] = 0
yp = f (xp) + υp, E[υp] = 0
Evaluated via regression with f (·) = β0φ0(·) + β1φ1(·) + · · ·
Selection of basis functions φ(·) crucial, especially in high dimensions
Di�cult to implement for generic products with scripted payo�s
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
General Bermudan Swaption Script
Figure: Example of a Numerix payo� script for a Bermudan swaption. All DISCOUNTING
variables are subjected to a regression as the algorithm works backward in time.
Andrew McClelland, Numerix xVA Pricing and Risk 10/13
Where Does Matlab Come In? 1
Clients using Numerix have their own views on how to aggregate
Instead of writing NX scripts & functions to do the maths use Matlab
Expose intermediate calcs to allow user logic
Many assumptions on counterparty behavior and default correlations
eg . �wrong-way risk" or WWR: exposures correlate with default prob
Subjective and clients want control over default prob trajectories
Andrew McClelland, Numerix xVA Pricing and Risk 11/13
Where Does Matlab Come In? 2
Also complications re. collateral arrangements and margining
Ratings triggers can force lower collateral thresholds and min transfers
Early-terminations as function of market conditions or credit health?
Similarly so for rolling of shorter-term trades
Collateral rehypothecation across counterparties for funding o�sets
Andrew McClelland, Numerix xVA Pricing and Risk 12/13
What Does the Future Hold?
The really di�cult calculations relate to portfolio-level e�ects
Looking for capital impacts (KVA) and initial margin impacts (MVA)
Capital and initial margin requirements are becoming more onerous18
Pricing these and/or optimizing against them is crucial
Also bene�ts to fully tracking cost of collateral transformation
18See eg . Basel FRTB (BCBS365) and Basel-IOSCO (BCBS317).Andrew McClelland, Numerix xVA Pricing and Risk 13/13
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