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The Martingale Approach to Operationaland Financial Hedging
Rene Caldentey Martin Haugh
Stern School of Business IE & OR
NYU Columbia University
Fuqua School of BusinessDuke University
October 2005.
Motivation
ProcurementSuppliers' Management
Inventory/ProductionCapacity/Processes
Product Design
DistributionPricing Policies
Demand Forecast
Corporation
The Martingale Approach to Operational and Financial Hedging 2
Motivation
ProcurementSuppliers' Management
Inventory/ProductionCapacity/Processes
Product Design
DistributionPricing Policies
Demand Forecast
Corporation
Problem:
Select an operational strategy and a financial strategy that optimize the value of thecorporation.
The Martingale Approach to Operational and Financial Hedging 2
Motivation
Operations and services models are now beginning to consider issues related to risk aversion and
hedging
There are many good reasons for hedging
– costs associated with financial distress
– taxes
– costs associated with raising capital
– principal-agent issues
– smoothing earnings for the Wall Street analysts!
And in practice corporations often do hedge
– not inconsistent with Modigliani - Miller theory of corporate finance
Is there a modelling framework that might be useful for operational and financial decision-making?
The Martingale Approach to Operational and Financial Hedging 3
Motivation
A Methodology that effectively integrates Operational and Financial activities by
– Maximizing the Economic Value of the corporation.
– Modeling the risk preferences of decision makers.
– Using financial markets for hedging purposes.
– Recognizing the “incompleteness”of the problem.
– Taking advantage of all available information.
The Martingale Approach to Operational and Financial Hedging 4
Motivation
A Methodology that effectively integrates Operational and Financial activities by
– Maximizing the Economic Value of the corporation.
– Modeling the risk preferences of decision makers.
– Using financial markets for hedging purposes.
– Recognizing the “incompleteness”of the problem.
– Taking advantage of all available information.
max Economic Valuesubject to problem dynamics
and subject to risk management constraint(s).
The Martingale Approach to Operational and Financial Hedging 4
Motivation
A Methodology that effectively integrates Operational and Financial activities by
– Maximizing the Economic Value of the corporation.
– Modeling the risk preferences of decision makers.
– Using financial markets for hedging purposes.
– Recognizing the “incompleteness”of the problem.
– Taking advantage of all available information.
max Economic Valuesubject to problem dynamics
and subject to risk management constraint(s).
Operational risk in customers’ taste, machine breakdowns, unreliable suppliers, etc...
Financial risk in exchange rates, commodity prices, interest rates, etc...
The Martingale Approach to Operational and Financial Hedging 4
Outline of Talk
Part I: The Modelling Framework
- Motivation for maximizing economic value of operating profits.
- Financial market & informational structure
Part II: Supply Contracts with Financial Hedging
- The Wholesale Price Contract with Budget Constraint
Part III: Models with Tail Constraints
- A Procurement Example
Conclusions & Further Research
The Martingale Approach to Operational and Financial Hedging 5
Part I
Modelling Framework
Financial Market & Information
The Martingale Approach to Operational and Financial Hedging 6
Motivating the Modelling Framework
Consider two series cash-flows arising from two operating policies I1 and I2:
C(1)
(I1) = (c(1)1 (I1), c
(1)2 (I1), . . . , c
(1)n (I1))
C(2)
(I2) = (c(2)1 (I2), c
(2)2 (I2), . . . , c
(2)n (I2))
If probability distribution of C(1) and C(2) identical then most operations models are indifferent
between the two.
However, if C(1) positively correlated with financial market for example, and C(2) negatively
correlated with financial market then economic value of C(2) greater than economic value of C(1).
– models should take this into account as they get ever more complex and include additional
sources of uncertainty
Do so by using an equivalent martingale measure, Q, or stochastic discount factor
– consistent with only a hedging motivation for financial trading
The Martingale Approach to Operational and Financial Hedging 7
The Modelling Framework
H(I) the time T cumulative payoff from some operating policy, I
– The operating policy may be static or dynamic.
The Martingale Approach to Operational and Financial Hedging 8
The Modelling Framework
H(I) the time T cumulative payoff from some operating policy, I
– The operating policy may be static or dynamic.
G(θ) the time T gain from a self-financing trading strategy, θ
The Martingale Approach to Operational and Financial Hedging 8
The Modelling Framework
H(I) the time T cumulative payoff from some operating policy, I
– The operating policy may be static or dynamic.
G(θ) the time T gain from a self-financing trading strategy, θ
Operational and financial hedging problem is
minI,G(θ)
EQ [H(I)]
subject to problem dynamics
and subject to risk management constraint(s) ≡R(H(I), G(θ)) ≤ 0 a.s.
EP [R(H(I), G(θ))] ≤ 0.
The Martingale Approach to Operational and Financial Hedging 8
The Modelling Framework
H(I) the time T cumulative payoff from some operating policy, I
– The operating policy may be static or dynamic.
G(θ) the time T gain from a self-financing trading strategy, θ
Operational and financial hedging problem is
minI,G(θ)
EQ [H(I)]
subject to problem dynamics
and subject to risk management constraint(s) ≡R(H(I), G(θ)) ≤ 0 a.s.
EP [R(H(I), G(θ))] ≤ 0.
consistent with only a hedging motivation for financial trading
– G(θ) a martingale under Q so EQ[G(θ)] = 0
– assuming initial capital assigned to hedging strategy is zero
The Martingale Approach to Operational and Financial Hedging 8
Financial Market Model
Probability space (Ω,F, P).
(W1t , W2t) a standard Brownian motion.
A single risky stock with price dynamics
dXt = µXt dt + σXt dW1t.
Cash account available with r ≡ 0.
Ft is the filtration generated by (W1t , W2t).
FXt is the filtration generated by Xt.
Operating profits, H(I) ∈ FT , a function of (W1t , W2t).
The gain process, G(θ)t of a self-financing trading strategy θt is
G(θ)t =
∫ t
0
θs dXs.
An equivalent martingale measure, Q, under which Xt and G(θ)t are martingales.
The Martingale Approach to Operational and Financial Hedging 9
Information
In general, operating profits are function of (Xt ,W2t), that is, H(I) ∈ FT .
The Martingale Approach to Operational and Financial Hedging 10
Information
In general, operating profits are function of (Xt ,W2t), that is, H(I) ∈ FT .
Incomplete Information:
– Demand, product quality, customer tastes not always observable.– Only information related to Xt is available.
⇒ Trading strategies must satisfy: θt ∈ FXt , t ∈ [0, T ].
The Martingale Approach to Operational and Financial Hedging 10
Information
In general, operating profits are function of (Xt ,W2t), that is, H(I) ∈ FT .
Incomplete Information:
– Demand, product quality, customer tastes not always observable.– Only information related to Xt is available.
⇒ Trading strategies must satisfy: θt ∈ FXt , t ∈ [0, T ].
Complete Information:
– The evolution of Xt and B2t are both available.
⇒ Trading strategies satisfy: θt ∈ Ft, t ∈ [0, T ].
The Martingale Approach to Operational and Financial Hedging 10
Part II
Supply Contracts with Financial Hedging
The Wholesale Price Contract with Budget Constaint
The Martingale Approach to Operational and Financial Hedging 11
The Wholesale Price Contract
ClearancePrice
! "
# ! $% ! &$
Non-Cooperative Operation:
Solution Concept: Stackelberg game.
1. At time t = 0, Manufacturer offers a wholesale price w to the Retailer.2. At time t = 0, Retailer orders a quantity q.3. At time t = T , a random clearance price P (q) is realized: P (q) = A− q.
The random price A is correlated to the financial market Xt.
Retailer operates under a budget constraint: wq ≤ B.
The Martingale Approach to Operational and Financial Hedging 12
Types of Contracts
timet = 0 t = T
!"Production takes place
The Martingale Approach to Operational and Financial Hedging 13
Types of Contracts
timet = 0 t = T
!"Production takes place
timet = 0 t = T
ττττ ττττ
t = τ
!ττττ
"#
Production takes place
$ % % & %'(( )
The Martingale Approach to Operational and Financial Hedging 13
Types of Contracts
timet = 0 t = T
!"Production takes place
timet = 0 t = T
ττττ ττττ
t = τ
!ττττ
"#
Production takes place
$ % % & %'(( )
timet = 0 t = T
ττττ ττττ
t = τ
!" #$% &ττττ ' ( )$ * *
ττττ ' (
Production takes placeFinancial hedging takes place
+% , , %- ,.// 0
The Martingale Approach to Operational and Financial Hedging 13
Types of Contracts
timet = 0 t = T
!"Production takes place
timet = 0 t = T
ττττ ττττ
t = τ
!ττττ
"#
Production takes place
$ % % & %'(( )
timet = 0 t = T
ττττ ττττ
t = τ
!" #$% &ττττ ' ( )$ * *
ττττ ' (
Production takes placeFinancial hedging takes place
+% , , %- ,.// 0
Remark: The time τ can be a decision variable: a deterministic time or a F Xτ -stopping time.
The Martingale Approach to Operational and Financial Hedging 13
Some Notation
∗) (Ω,F,Q) probability space.
∗) Xt: Time t value of a Q-martingale tradable security (t ∈ [0, T ]).
∗) Ft = σ(Xs ; 0 ≤ s ≤ t) filtration generated by Xt with FT ⊆ F .
∗) EQτ [E] := EQ[E|Fτ ] for all E ∈ F .
∗) P (q) = A− q: retail price at time T with A ∈ F .
∗) Aτ = EQ[A|Fτ ] for any Ft-stopping time τ ≤ T .
∗) cτ : per unit manufacturing cost at time τ ∈ [0, T ].
∗) wτ ∈ Fτ : manufacturer’s wholesale price menu.
∗) qτ ∈ Fτ : retailer’s ordering quantity menu.
∗) Gτ ∈ Fτ : retailer’s trading gains (or losses) with EQ[Gτ ] = 0.
∗) Budget constraint: wτ qτ ≤ Bτ := B + Gτ .
Assumption. For all τ ∈ [0, T ], Aτ ≥ cτ .
The Martingale Approach to Operational and Financial Hedging 14
Flexible Contract
Consider a fixed τ ∈ [0, T ].
Step 1: At t = 0, the manufacturer offers a wholesale menu wτ ∈ Fτ .
Step 2: A retailer, with no access to the financial market, decides the ordering level qτ ∈ Fτ solving
ΠFR(wτ) = EQ0
[maxqτ ≥0
EQτ [(A− qτ − wτ) qτ ]
]
subject to wτ qτ ≤ B, for all ω ∈ Ω.
The optimal solution (retailer’s reaction) is
q(wτ) = min
(Aτ − wτ
2
)+
,B
wτ
.
Step 3: The manufacturer problem is (Stackelberg leader)
ΠFM = EQ0
[maxwτ≥cτ
(wτ − cτ) qτ(wτ)]
.
The Martingale Approach to Operational and Financial Hedging 15
Flexible Contract
Proposition. (Flexible Contract Solution)
Under Assumption , the equilibrium solution for the flexible contract is
wFτ =
Aτ + δ Fτ
2and q
Fτ =
Aτ − δ Fτ
4,
where
δFτ := max
cτ ,
√(A2
τ − 8 B)+
.
The equilibrium expected payoffs of the players are then given by
ΠFM|τ =
(Aτ + δ Fτ − 2 cτ) (Aτ − δ F
τ)
8and Π
FR|τ =
(Aτ − δ Fτ)
2
16.
Remarks:
-) δ Fτ is a modified production cost (≥ cτ) that is induced by a limited budget B.
-) w Fτ decreases in B and q F
τ , Π FM|τ and Π F
R|τ increase in B.
The Martingale Approach to Operational and Financial Hedging 16
Flexible Contract vs. Simple Contract
Define wF:= EQ0 [w
Fτ ], q
F:= EQ0 [q
Fτ ], Π
FM := EQ0 [Π
FM|τ ] and Π
FR := EQ0 [Π
FR|τ ].
Proposition. Suppose that B ≤ A2τ−c2τ8 almost surely. Then
wF ≤ w
S, q
F ≥ qS, Π
FM ≤ Π
SM and Π
FR ≥ Π
SR.
However, if B ≥ max
A2
τ−c2τ8 ,
A2−c208
almost surely then
wF= w
S+
cτ − c0
2and q
F= q
S − cτ − c0
4
and ΠFM ≥ Π
SM and Π
FR ≥ Π
SR if and only if EQ0 [(Aτ − cτ)
2] ≥ (A− c0)
2.
The Martingale Approach to Operational and Financial Hedging 17
Flexible Contract vs. Simple Contract
0 0.6 1.21
1.2
1.4
1.6
1.8
2Wholesale Price
0 0.6 1.20
0.1
0.2
0.3
0.4
0.5Ordering Level
0 0.6 1.2
0.5
1
1.5
2Flexible vs. Simple
0 0.6 1.21
1.2
1.4
1.6
1.8
2
0 0.6 1.20
0.1
0.2
0.3
0.4
0.5
Budget (B) 0 0.6 1.2
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Case 1
Case 2
Flexible
Simple
Flexible
Simple
Flexible
Flexible
Simple
Simple
ΠRF/Π
RS
ΠRF/Π
RS
ΠPF/Π
PS
ΠPF/Π
PS
Aτ ∼ Uniform[1, 3], c0 = 0.3, cτ = 0.35 (case 1) and cτ = 0.7 (case 2).
The Martingale Approach to Operational and Financial Hedging 18
Flexible Contract: Efficiency
0 0.5 10.3
0.35
0.4
0.45
0.5
0.55
0 0.5 12
2.5
3
3.5
0 0.5 10.2
0.3
0.4
0.5
0.6
0.7
0 0.5 10.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0 0.5 11.3
1.4
1.5
1.6
1.7
1.8
0 0.5 10.15
0.2
0.25
0.3
0.35
0.4
Budget (B)
QFτ WFτ PFτ
Aτ ≥ 3 cτ
Aτ ≤ 3 cτ
Aτ = 2, cτ = 0.6 (top) and cτ = 1.2 (bottom).
The Martingale Approach to Operational and Financial Hedging 19
Flexible Contract with Financial Hedging
timet = 0 t = T
ττττ ττττ
t = τ
!" #$% &ττττ ' ( )$ * *
ττττ ' (
Production takes placeFinancial hedging takes place
+% , , %- ,.// 0
The Martingale Approach to Operational and Financial Hedging 20
Flexible Contract with Financial Hedging
timet = 0 t = T
ττττ ττττ
t = τ
!" #$% &ττττ ' ( )$ * *
ττττ ' (
Production takes placeFinancial hedging takes place
+% , , %- ,.// 0
Step 1: At t = 0, and for a fixed τ ≤ T , the manufacturer offers a price menu wτ ∈ F Xτ .
The Martingale Approach to Operational and Financial Hedging 20
Flexible Contract with Financial Hedging
timet = 0 t = T
ττττ ττττ
t = τ
!" #$% &ττττ ' ( )$ * *
ττττ ' (
Production takes placeFinancial hedging takes place
+% , , %- ,.// 0
Step 1: At t = 0, and for a fixed τ ≤ T , the manufacturer offers a price menu wτ ∈ F Xτ .
Step 2: In response, at t = 0, the retailer selects an optimal ordering menu q∗τ(wτ) ∈ F Xτ solving
ΠHR(wτ) = max
qτ≥0, GτEQ [(A− qτ) qτ − wτ qτ ]
subject to wτ qτ ≤ B + Gτ , for all ω ∈ Ω
EQ[Gτ ] = 0.
The Martingale Approach to Operational and Financial Hedging 20
Flexible Contract with Financial Hedging
timet = 0 t = T
ττττ ττττ
t = τ
!" #$% &ττττ ' ( )$ * *
ττττ ' (
Production takes placeFinancial hedging takes place
+% , , %- ,.// 0
Step 1: At t = 0, and for a fixed τ ≤ T , the manufacturer offers a price menu wτ ∈ F Xτ .
Step 2: In response, at t = 0, the retailer selects an optimal ordering menu q∗τ(wτ) ∈ F Xτ solving
ΠHR(wτ) = max
qτ≥0, GτEQ [(A− qτ) qτ − wτ qτ ]
subject to wτ qτ ≤ B + Gτ , for all ω ∈ Ω
EQ[Gτ ] = 0.
Step 3: The manufacturer selects the optimal wholesale price menu w∗τ solving
ΠHM(wτ) = max
wτEQ
[wτ q
∗τ(wτ)− cτ q
∗τ(wτ)
].
The Martingale Approach to Operational and Financial Hedging 20
Flexible Contract with Financial Hedging
Proposition. (Retailer’s Optimal Strategy)
Let Qτ , X and X c be defined as follows
Qτ ,(
Aτ − wτ
2
)+
, X , ω ∈ Ω : B ≥ Qτ wτ , and X c , Ω− X .
The Martingale Approach to Operational and Financial Hedging 21
Flexible Contract with Financial Hedging
Proposition. (Retailer’s Optimal Strategy)
Let Qτ , X and X c be defined as follows
Qτ ,(
Aτ − wτ
2
)+
, X , ω ∈ Ω : B ≥ Qτ wτ , and X c , Ω− X .
Case 1: Suppose that EQ [Qτ wτ ] ≤ B. Then q∗τ(wτ) = Qτ and there are infinitely many
choices of the optimal claim, Gτ . One natural choice is to take
Gτ = [Qτ wτ − B] ·
δ if ω ∈ X1 if ω ∈ X c
δ ,∫Xc [Qτ wτ − B] dQ∫X [B −Qτ wτ ] dQ
.
The Martingale Approach to Operational and Financial Hedging 21
Flexible Contract with Financial Hedging
Proposition. (Retailer’s Optimal Strategy)
Let Qτ , X and X c be defined as follows
Qτ ,(
Aτ − wτ
2
)+
, X , ω ∈ Ω : B ≥ Qτ wτ , and X c , Ω− X .
Case 1: Suppose that EQ [Qτ wτ ] ≤ B. Then q∗τ(wτ) = Qτ and there are infinitely many
choices of the optimal claim, Gτ . One natural choice is to take
Gτ = [Qτ wτ − B] ·
δ if ω ∈ X1 if ω ∈ X c
δ ,∫Xc [Qτ wτ − B] dQ∫X [B −Qτ wτ ] dQ
.
Remark: In this case, it is possible to completely eliminate the budget constraint by trading in the
financial market.
The Martingale Approach to Operational and Financial Hedging 21
Flexible Contract with Financial Hedging
Proposition. (Continuation)
Case 2: Suppose that B < EQ [Qτ wτ ]. Then
qτ(wτ) =
(Aτ − wτ (1 + λ)
2
)+
where λ ≥ 0 solves EQ[
wτ
(Aτ − wτ (1 + λ)
2
)+]
= B.
The Martingale Approach to Operational and Financial Hedging 22
Flexible Contract with Financial Hedging
Proposition. (Continuation)
Case 2: Suppose that B < EQ [Qτ wτ ]. Then
qτ(wτ) =
(Aτ − wτ (1 + λ)
2
)+
where λ ≥ 0 solves EQ[
wτ
(Aτ − wτ (1 + λ)
2
)+]
= B.
Proposition. (Producer’s Optimal Strategy and the Stackelberg Solution)
Let φ∗ , inf
φ ≥ 1 such that EQ
[(A2
τ−(φ cτ )2
8
)+]≤ B
.
Then, w∗τ = Aτ+φ∗ cτ
2 and q∗τ =(
Aτ−φ∗ cτ4
)+
and the players’ expected payoffs satisfy
ΠHM|τ =
(Aτ + φ∗ cτ − 2cτ) (Aτ − φ∗ cτ)+
8and Π
HR|τ =
((Aτ − φ∗ cτ)+)2
16.
The Martingale Approach to Operational and Financial Hedging 22
Flexible Contract with Financial Hedging
Proposition. (Continuation)
Case 2: Suppose that B < EQ [Qτ wτ ]. Then
qτ(wτ) =
(Aτ − wτ (1 + λ)
2
)+
where λ ≥ 0 solves EQ[
wτ
(Aτ − wτ (1 + λ)
2
)+]
= B.
Proposition. (Producer’s Optimal Strategy and the Stackelberg Solution)
Let φ∗ , inf
φ ≥ 1 such that EQ
[(A2
τ−(φ cτ )2
8
)+]≤ B
.
Then, w∗τ = Aτ+φ∗ cτ
2 and q∗τ =(
Aτ−φ∗ cτ4
)+
and the players’ expected payoffs satisfy
ΠHM|τ =
(Aτ + φ∗ cτ − 2cτ) (Aτ − φ∗ cτ)+
8and Π
HR|τ =
((Aτ − φ∗ cτ)+)2
16.
Remark: When q∗τ = 0, the manufacturer decides to overcharge the retailer making the supply chain
non-operative. This is never the case if the retailer does not have not access to the financial market.
The Martingale Approach to Operational and Financial Hedging 22
Flexible Contract with Financial HedgingProposition. The manufacturer always prefers the H-contract to the F-Contract. On the other hand,
the retailer’s preferences are
!"#$ %"&"'($
The Martingale Approach to Operational and Financial Hedging 23
Flexible Contract with Financial HedgingProposition. The manufacturer always prefers the H-contract to the F-Contract. On the other hand,
the retailer’s preferences are
!"#$ %"&"'($
0 0.5 1 1.5 2
1.2
1.4
1.6
1.8
2
2.2
2.4
Wholesale Price
Budget (B)0 0.5 1 1.5 2
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4Ordering Level
0 0.5 1 1.5 20
0.05
0.1
0.15
0.2
0.25
0.3
0.35Producer’s Payoff
0 0.5 1 1.5 20
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18Retailer’s Payoff
Budget (B)
Budget (B)Budget (B)
H−Contract
F−Contract
H−Contract
F−Contract
F−Contract F−Contract
H−Contract
H−Contract
The Martingale Approach to Operational and Financial Hedging 23
Flexible Contract with Financial HedgingEfficiency
On path-by-path basis, the Centralized system is not necessarily more efficient thanthe Decentralized Supply Chain!
∃ω ∈ Ω such that q HC|τ = 0 and q H
τ > 0.
Remarks: This is never the case under a Flexible Contract without Hedging.
The Martingale Approach to Operational and Financial Hedging 24
Flexible Contract with Financial HedgingEfficiency
On path-by-path basis, the Centralized system is not necessarily more efficient thanthe Decentralized Supply Chain!
∃ω ∈ Ω such that q HC|τ = 0 and q H
τ > 0.
Remarks: This is never the case under a Flexible Contract without Hedging.
On average, the Centralized solution is more efficient than the Decentralizedsolution.
EQ0[qHC|τ ] ≥ EQ0[q H
τ ].
The Martingale Approach to Operational and Financial Hedging 24
Summary
Simple extension to the traditional wholesale contract.
The Martingale Approach to Operational and Financial Hedging 25
Summary
Simple extension to the traditional wholesale contract.
The proposed procurement contracts uses the Financial Market as:
– A source of public information upon which contracts can be written.
– A means for financial hedging to mitigate the impact of the budget constraint.
The Martingale Approach to Operational and Financial Hedging 25
Summary
Simple extension to the traditional wholesale contract.
The proposed procurement contracts uses the Financial Market as:
– A source of public information upon which contracts can be written.
– A means for financial hedging to mitigate the impact of the budget constraint.
Consistent with the notions of production postponement and demand forecast.
The Martingale Approach to Operational and Financial Hedging 25
Summary
Simple extension to the traditional wholesale contract.
The proposed procurement contracts uses the Financial Market as:
– A source of public information upon which contracts can be written.
– A means for financial hedging to mitigate the impact of the budget constraint.
Consistent with the notions of production postponement and demand forecast.
Managerial Insights:
– Manufacturer and Retailer incentives are not always aligned as a function of B.
– Manufacturer prefers retailers that have access to the financial market.
– With hedging, the supply chain might not operate in some states ω ∈ Ω.
– In some cases, financial hedging eliminates the budget constraint.
– Optimal time τ of the contract balances Var(Aτ) and cτ .
The Martingale Approach to Operational and Financial Hedging 25
Summary
Simple extension to the traditional wholesale contract.
The proposed procurement contracts uses the Financial Market as:
– A source of public information upon which contracts can be written.
– A means for financial hedging to mitigate the impact of the budget constraint.
Consistent with the notions of production postponement and demand forecast.
Managerial Insights:
– Manufacturer and Retailer incentives are not always aligned as a function of B.
– Manufacturer prefers retailers that have access to the financial market.
– With hedging, the supply chain might not operate in some states ω ∈ Ω.
– In some cases, financial hedging eliminates the budget constraint.
– Optimal time τ of the contract balances Var(Aτ) and cτ .
Extensions:
– Other types of contracts: quantity discount, buy-back, etc.
– Include other sources of uncertainty: exchange rates, interest rates, credit risk.
The Martingale Approach to Operational and Financial Hedging 25
Part III
Models with Tail Constraints
Example: A Procurement Model
The Martingale Approach to Operational and Financial Hedging 26
Problem Formulation
maxI,θ
EQ[H(I)]
subject to EP[R(H(I) + G(θ))] ≥ H.
The Martingale Approach to Operational and Financial Hedging 27
Problem Formulation
maxI,θ
EQ[H(I)]
subject to EP[R(H(I) + G(θ))] ≥ H.
1−η1−η1−η1−η
η
!""# $%&'
The Martingale Approach to Operational and Financial Hedging 27
Problem Formulation
maxI,θ
EQ[H(I)]
subject to EP[R(H(I) + G(θ))] ≥ H.
1−η1−η1−η1−η
η
!""# $%&'
Value-at-Risk (VaRη): Hη ≥ H.
The Martingale Approach to Operational and Financial Hedging 27
Problem Formulation
maxI,θ
EQ[H(I)]
subject to EP[R(H(I) + G(θ))] ≥ H.
1−η1−η1−η1−η
η
!""# $%&'
Value-at-Risk (VaRη): Hη ≥ H.
Conditional Value-at-Risk (CVaRη): EP[H(I) |H(I) ≤ Hη] ≥ H.
The Martingale Approach to Operational and Financial Hedging 27
Problem Formulation
maxI,θ
EQ[H(I)]
subject to EP[R(H(I) + G(θ))] ≥ H.
1−η1−η1−η1−η
η
!""# $%&'
Value-at-Risk (VaRη): Hη ≥ H.
Conditional Value-at-Risk (CVaRη): EP[H(I) |H(I) ≤ Hη] ≥ H.
Mean & Standard-Deviation (MStdη): EP[H(I)]−√
η1−η
√Var(H(I)) ≥ H.
The Martingale Approach to Operational and Financial Hedging 27
Tail Constraints: Bounds
Rockafellar and Ursayev (2002):
CVaRη(X) = minζ
ζ +
1
1− ηEP[(X − ζ)
+]
.
The Martingale Approach to Operational and Financial Hedging 28
Tail Constraints: Bounds
Rockafellar and Ursayev (2002):
CVaRη(X) = minζ
ζ +
1
1− ηEP[(X − ζ)
+]
.
Define EP[X] = µX and Var(X) = σ2X then Gallego (1992):
EP[(X − ξ)
+]≤
√σ2
X + (ξ − µX)2 − (ξ − µX)
2.
The Martingale Approach to Operational and Financial Hedging 28
Tail Constraints: Bounds
Rockafellar and Ursayev (2002):
CVaRη(X) = minζ
ζ +
1
1− ηEP[(X − ζ)
+]
.
Define EP[X] = µX and Var(X) = σ2X then Gallego (1992):
EP[(X − ξ)
+]≤
√σ2
X + (ξ − µX)2 − (ξ − µX)
2.
Combining these results we get
CVaRη(X) ≤ µX +
√η
1− ησX , MStdη(X).
The Martingale Approach to Operational and Financial Hedging 28
Tail Constraints: Bounds
Rockafellar and Ursayev (2002):
CVaRη(X) = minζ
ζ +
1
1− ηEP[(X − ζ)
+]
.
Define EP[X] = µX and Var(X) = σ2X then Gallego (1992):
EP[(X − ξ)
+]≤
√σ2
X + (ξ − µX)2 − (ξ − µX)
2.
Combining these results we get
CVaRη(X) ≤ µX +
√η
1− ησX , MStdη(X).
Tail Constraint Ordering
VaRη ≥ CVaRη ≥ MStdη.
The Martingale Approach to Operational and Financial Hedging 28
Problem Formulation
For some η ∈ [0, 1] and H, we would like to solve
maxI,G(θ)
EQ [H(I)]
subject to EP[H(I) + G(θ)]−√(
η
1− η
)Var (H(I) + G(θ)) ≥ H,
EQ[G(θ)] = 0 and θt ∈ FXt︸ ︷︷ ︸
Incomplete Inf.
or θt ∈ Ft︸ ︷︷ ︸Complete Inf.
.
The Martingale Approach to Operational and Financial Hedging 29
Problem Formulation
For some η ∈ [0, 1] and H, we would like to solve
maxI,G(θ)
EQ [H(I)]
subject to EP[H(I) + G(θ)]−√(
η
1− η
)Var (H(I) + G(θ)) ≥ H,
EQ[G(θ)] = 0 and θt ∈ FXt︸ ︷︷ ︸
Incomplete Inf.
or θt ∈ Ft︸ ︷︷ ︸Complete Inf.
.
Two-step Optimization:
Step 1: (Hedging Policy) For a fixed operating policy, I, we solve the hedging problem.
V (I) , maxG(θ)
MStdη(H(I) + G(θ)) subject to EQ[G(θ)] = 0.
The Martingale Approach to Operational and Financial Hedging 29
Problem Formulation
For some η ∈ [0, 1] and H, we would like to solve
maxI,G(θ)
EQ [H(I)]
subject to EP[H(I) + G(θ)]−√(
η
1− η
)Var (H(I) + G(θ)) ≥ H,
EQ[G(θ)] = 0 and θt ∈ FXt︸ ︷︷ ︸
Incomplete Inf.
or θt ∈ Ft︸ ︷︷ ︸Complete Inf.
.
Two-step Optimization:
Step 1: (Hedging Policy) For a fixed operating policy, I, we solve the hedging problem.
V (I) , maxG(θ)
MStdη(H(I) + G(θ)) subject to EQ[G(θ)] = 0.
Step 2: (Operational Policy) Then, we compute the optimal operational policy solving
maxIEQ[H(I)] subject to V (I) ≥ H.
The Martingale Approach to Operational and Financial Hedging 29
Incomplete Information Model: Step 1
Theorem. (Incomplete Information Hedging)
Let us denote by π the Radon-Nikodym derivative of Q with respect to P. Suppose that the hedging
strategy θ is restricted to be FXT -measurable. Then, the following two cases are possible:
Case 1: If η ≥ EP[π2]−1
EP[π2]then
V (I) = EQ[H(I)]−[(
η − (1− η) (EP[π2]− 1)
1− η
)Var(H(I)− EP[H(I)|FX
T ])
]12
.
Case 2: If η < EP[π2]−1
EP[π2]then
V (I) = +∞.
Remark: In Case 2, financial trading has removed the risk management constraint.
The Martingale Approach to Operational and Financial Hedging 30
Incomplete Information Model: Step 2
Case 1: If η ≥ EP[π2]−1
EP[π2], then the (financially hedged) operational problem is
maxI
EQ[H(I)]
s.t. EQ[H(I)]−[(
η − (1− η) (EP[π2]− 1)
1− η
)Var(H(I)− EP[H(I)|FX
T ])
]12
≥ H.
Case 2: If η < EP[π2]−1
EP[π2], then the (financially hedged) operational problem is
maxI
EQ[H(I)]
Remarks:
X Case 2 is the standard risk neutral operational model but under the “appropriate” EMM.
X If H(I) ∈ FXT then Case 1 reduces to
maxI
EQ[H(I)] s.t. EQ[H(I)] ≥ H.
The Martingale Approach to Operational and Financial Hedging 31
A Procurement Example
!
0 T
The Retailer’s profit is H(I) = (P (I)− c) I.
I : Ordering Level at time 0.
P (I) : Clearance Price at time T as a function of I.
c : Per unit purchasing cost.
Problem:maxI,G
EQ[H(I)] subject to MStdη(H(I) + G) ≥ H.
Assumptions: Xt ∼ (µ, σ)-GBM : dXt = µ Xt dt + σ Xt dW1t.
Linear Demand Model: P (I) = A− I, A = ζ + γ ln(XT ) + α W2T .
The Martingale Approach to Operational and Financial Hedging 32
A Procurement Example (contd’)
Solution without Financial Hedging
0 800 1600−2
0
10
20x 10
5
Objective: EQ[H(I)]
MStdη Constraint
No Hedging
I*
H
Ic
The Martingale Approach to Operational and Financial Hedging 33
A Procurement Example (contd’)
Solution with Financial Hedging if η ≥ EP[π2]−1
EP[π2]
0 800 1600−2
0
10
20x 10
5
Objective: EQ[H(I)]
MStdη Constraint
No Hedging
I*
H
MStdη Constraint
With Incomplete Hedging
MStdη Constraint
With Complete Hedging
The Martingale Approach to Operational and Financial Hedging 34
A Procurement Example (contd’)
0.4 0.5 0.6 0.7 0.8 0.9 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
η
Hoptc
/Hoptu
0 0.5 1 1.5 20
0.2
0.4
0.6
0.8
1
T
Hoptc
/Hoptu
No Hedging
Incomplete
Complete
Incomplete
No Hedging
Complete
The Martingale Approach to Operational and Financial Hedging 35
Conclusions
A modelling framework for selecting operating and financial hedging strategies
– Consistent with maximizing economic value of the firm.
– Models risk preferences using risk management constraints.
– The only motivation for financial trading is hedgingin particular, no profit motivation for hedging.
– Structural properties result in considerable tractability
– Considers different information structures.
Dynamic trading
– Reduces, and in some cases, eliminates the negative effects of risk constraints.
– Improves the overall performance/efficiency of the operations.
Further Research
The Martingale Approach to Operational and Financial Hedging 36