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Optimal Investment Strategies Under the Relative Performance in
Jump-Diffusion Markets
22nd ECMI Conference on Industrial and Applied Mathematics, 26-30 June 2023 -
Wroclaw, Poland
Burcu Aydoğan
(Joint work with Mogens Steffensen in the University of Copenhagen)
RWTH Aachen University
June 26, 2023
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 1 / 40
Outline
1 Introduction
2 Framework
3 Concluding Remarks
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 2 / 40
Introduction
Our problem: Determine the optimal investment strategies of one agent and (a large
group of agents) having CRRA utilities under relative performance concerns.
There is a strategic interaction between the agent and the group which is caused by
their relative performances.
We solve two classical Merton problems to determine what the group does and the
agent’s optimal strategy relative to the group’s performance.
There are some studies which revealed the significance of the relative performance
concerns on human behaviors, see for instance [3] and [5].
In our framework, the stock price is defined on jump-diffusion markets where we
both consider the upward and downward jumps in the numerical observations.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 3 / 40
Basak and Makarov [1] work on a portfolio choice problem with a competition
between two risk-averse portfolio managers where the stock follows geometric
Brownian motion.
Espinosa and Touzi [4] consider n interacting agents maximizing the difference
between an agent’s wealth and average wealth of other agents’ wealth.
Lacker and Zariphopoulou [7] work on an optimal portfolio management problem for
interacting n interacting agents with both CARA and CRRA utilities. They obtain
equilibrium strategies for both n agents and mean-field games.
Lacker and Soret [6] extend the CRRA model developed by Lacker and
Zariphopoulou [7] for a continuous time-dependent problem including relative
performances.
Reis and Platonov [8] develop equilibrium strategies using forward utilities of CARA
type.
Bäuerle and Göll [2] obtain Nash equilibrium investment strategies under the
strategic interactions of n agents investigating the influence of the price impact on
the equilibrium.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 4 / 40
Our work is a special case of the paper Lacker and Zariphopoulou [7] in the
following directions:
(i) We simplify their mean-field equilibrium results by considering only one agent and a
group of agents.
(ii) In our framework, the stock price is followed in a jump-diffusion market as follows:
dSt = St

µdt + νdWt + σdBt − εdNt − ε̃dÑt

with constant parameters µ, ν, σ  0; the constant jump sizes ε, ε̃; two independent
standard Brownian motions Wt and Bt and two independent Poisson processes Nt and
Ñt.
(iii) Moreover, we assume that the agents in the market are homogeneous in their
risk-aversions and relative performances as a special case.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 5 / 40
Framework
We define a complete probability space (Ω, F, P) with a sample space Ω, a filtration
F = {Ft}0≤t≤T and a probability measure P.
The agent and the group trade using self-financing strategies πt and π̂t which
represent the optimal proportional allocations in the portfolio, respectively.
Let X and Y denote the wealth of the agent and the group. We suppose that they
are generated by the dynamics,
dXt = πtXt

µdt + νdWt + σdBt − εdNt − ε̃dÑt

,
X0 = x0;
dYt = π̂tYt

µ̂dt + σ̂dBt − ε̂dNt

,
Y0 = y0. (1)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 6 / 40
In this setup,
(i) µ, µ̂ are the constant drift parameters;
(ii) ν, σ, σ̂  0 are the constant volatility parameters;
(iii) Wt and Bt are independent standard Brownian motions; W is an idiosyncratic noise
and B is the common noise;
(iv) ε, ε̃, ε̂ are the constant jump sizes;
(v) Nt and Ñt are two independent Poisson processes with the constant intensities λ and
λ̃, respectively;
(vi) the allocations π and π̂ determine the proportion of the agent’s wealth and the group’s
wealth, respectively.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 7 / 40
Optimal control problem for the group
The utility function of the group:
V (Y ) =
1
1 − η
Y 1−η
where η  0, η ̸= 1 is the risk-aversion of the group.
The optimization problem of the group:
u(y, t) = sup
π̂∈Â
E[V (Y )] = sup
π̂∈Â
E[V (y) | Y0 = y] (2)
where  is the set of admissible strategies which is defined as
 =

π̂ : π̂t ∈ Ft, E
Z T
0
|π̂t|2
dt

 ∞ and Yt  0, t  0

.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 8 / 40
The Hamilton-Jacobi-Bellman (HJB) equation for the value function (2):
ut + sup
π̂∈A

µ̂π̂ yuy +
1
2
σ̂2
π̂2
y2
uyy + λ

u(y − π̂yε̂, t) − u(y, t)

= 0 (3)
for (y, t) ∈ R+ × [0, T] with the terminal condition
u(y, T) =
1
1 − η
y1−η
.
The resulting equation for π̂:
µ̂ − σ̂2
π̂η − λε̂(1 − π̂ε̂)−η
= 0. (4)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 9 / 40
Optimal control problem for the agent
The utility function of the agent:
U(X, Y ) =
1
1 − γ

XY −θ
1−γ
(5)
where γ  0, γ ̸= 1 is the risk-aversion of the agent and 0 ≤ θ ≤ 1 specifies the
influence from the group Y on the utility of the agent.
Some comments on the utility function:
When θ = 0, the group’s performance does not impact the agent’s performance.
When θ = 1, the utility function (5) is
U(X, Y ) =
1
1 − γ

X
Y
1−γ
,
such that the utility is gained from a direct relative performance between the agent
and the group.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 10 / 40
The stochastic optimal control problem of the agent:
w(x, y, t) = sup
π∈A
E [U(X(T), Y (T)) | X0 = x, Y0 = y]
= sup
π∈A
E

1
1 − γ

X(T)Y −θ
(T)
1−γ
| X0 = x, Y0 = y

, (6)
where A is the set of admissible strategies for the optimal strategies π which is given
as
A =

π : πt ∈ Ft, E
Z T
0
|πt|2
dt

 ∞ and Yt  0, t  0

.
The Hamilton-Jacobi-Bellman (HJB) equation:
0 =wt + µ̂yπ̂wy +
1
2
σ̂2
y2
π̂2
wyy + sup
π∈A

π (µxwx + σσ̂xyπ̂wxy) +
1
2
v2
+ σ2

π2
x2
wxx
+ λ

w(x − πxε, y − π̂yε̂, t) − w(x, y, t)

+ λ̃

w(x − πxε̃, y, t) − w(x, y, t)
o
(7)
for (x, y, t) ∈ R+ × R+ × [0, T] with the final condition
w(x, y, T) =
1
1 − γ

xy−θ
1−γ
.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 11 / 40
The ansatz w(x, y, t) = g(t) 1
1−γ
xy−θ
1−γ
yields the ODE
g′
(t) + ρ̃g(t) = 0
where
ρ̃ = −µ̂π̂θ(1 − γ) −
1
2
σ̂2
π̂2
θ(θγ − θ − 1)(1 − γ)
+ sup
π∈A

µπ(1 − γ) − σσ̂π̂θ(1 − γ)2
π −
1
2
(ν2
+ σ2
)π2
γ(1 − γ)
+λ

(1 − πε)(1 − π̂ε̂)−θ
1−γ
− 1

+ λ̃ (1 − πε̃)1−γ
− 1


.
The resulting equation for π:
µ − σσ̂π̂θ(1 − γ) − (ν2
+ σ2
)πγ − λ(1 − πε)−γ
ε(1 − π̂ϵ̂)−θ(1−γ)
− λ̃(1 − πε̃)−γ
ε̃ = 0.
(8)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 12 / 40
Optimal strategies of the group:
Remember that the resulting equation for π̂ is
µ̂ − σ̂2
π̂η − λε̂(1 − π̂ε̂)−η
= 0.
The pure diffusion case (ε̂ = 0):
π̂∗
=
µ̂
σ̂2η
, (9)
which is the classical Merton optimal strategy.
The pure jump case (σ̂ = 0):
π̂∗
=
1
ε̂
−
( µ̂
λε̂
)
− 1
η
ε̂
. (10)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 13 / 40
Optimal strategies of the agent:
Remember that the resulting equation for π is
µ − σσ̂π̂θ(1 − γ) − (ν2
+ σ2
)πγ − λ(1 − πε)−γ
ε(1 − π̂ϵ̂)−θ(1−γ)
− λ̃(1 − πε̃)−γ
ε̃ = 0. (11)
1 The pure diffusion case (ε = ε̃ = 0):
π∗
=
1
γ
µ − σσ̂π̂θ( 1
γ
− 1)
v2 + σ2
(12)
where 1
γ
is defined as the risk-tolerance parameter of the agent.
We discuss this result in relation to certain results achieved by Lacker and
Zariphopoulou [7] where they obtain a Mean Field Equilibrium strategy under relative
performances.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 14 / 40
Lemma
Assuming that the agent has the optimal strategy π given by (12), we recover the Mean
Field Equilibrium strategy in Lacker and Zariphopoulou [7].
Proof.
The Mean Field Equilibrium strategy formula in Lacker and Zariphopoulou [7] reads
π∗
= δ ·
µ
σ2 + v2
− θ(δ − 1)
σ
σ2 + v2
·
φ
1 + ψ
,
where the constants φ and ψ are defined as
φ := E

δ
µσ
σ2 + ν2
#
and ψ := E

θ(δ − 1)
σ2
σ2 + ν2
#
,
the expectations are essentially averages over individuals in their mean-field
approach and δ = 1/γ.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 15 / 40
Proof (Cont.)
The task is to develop the mean-field version of σ̂π̂.
Multiply both sides of (12) by σ to obtain
σπ∗
=
1
γ
µσ
v2 + σ2
−
σ2
σ̂π̂θ( 1
γ
− 1)
v2 + σ2
. (13)
Now, take the average over all individuals on both sides and denote the average over
individuals as a plain expectation. Then, the left-hand side becomes
σ̂π̂ = E[σπ∗
],
and the right-hand side becomes
E
 1
γ
µσ
v2 + σ2
#
− E

σ2
σ̂π̂θ( 1
γ
− 1)
v2 + σ2
#
= ψ + σ̂π̂φ.
Equating the two sides and solving for σ̂π̂ gives
σ̂π̂ =
ψ
1 + φ
. (14)
Plugging (14) back into (12) gives exactly the Mean Field Equilibrium strategy in
Lacker and Zariphopoulou [7].
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 16 / 40
Single stock case:
Lemma
Assume that µ̂ = µ, σ̂ = σ and v = 0. Then, the optimal strategy reads as
π∗
=
µ
σ2

 1
γ
−
E
h
1
γ
i
1 + E
h
θ

1
γ
− 1
iθ

1
γ
− 1


 . (15)
Proof.
When µ̂ = µ, σ̂ = σ and v = 0, (12) simplifies to
π∗
=
1
γ
µ
σ2
− π̂θ

1
γ
− 1

. (16)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 17 / 40
Proof (Cont.)
Averaging over both sides gives
π̂ = E

1
γ

µ
σ2
− π̂E

θ

1
γ
− 1

.
Solved for π̂ gives
π̂ =
E
h
1
γ
i
µ
σ2
1 + E
h
θ

1
γ
− 1
i.
Then, plugged into π∗
in (16) gives us (15).
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 18 / 40
δ
0.0
0.5
1.0
1.5
2.0
̄
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
3
4
5
6
7
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
2
4
6
8
10
Figure 1: (Single stock case) Optimal strategy π∗ versus θ̄ = E[θ] and δ = 1
γ
in Lacker and
Zariphopoulou [7] with θ = 3
4
and δ̄ = E
h
1
γ
i
= 2 and our strategy π∗ in (15) versus θ and 1
γ
with E[θ] = 3
4
and E
h
1
γ
i
= 2 with the common parameters µ = 5, σ = 1.
Note that we assume θ and 1
γ
are uncorrelated to generate the above results.
When θ = 0, then π∗
increases linearly.
When θ = 1, π∗
is independent of γ.
When γ  1, π∗
increases in θ.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 19 / 40
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
δ = 1
γ
2
3
4
5
6
7
8
π
theta1=0.25
theta2=0.6
theta3=0.9
Figure 2: Optimal investment strategy versus δ = 1
γ
for different θ values.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 20 / 40
Homogeneous agents case:
The agents are homogeneous in their risk-aversions and relative performances, i.e.
E
h
1
γ
i
= 1
γ
and E[θ] = θ.
By this assumption, (15) turns out to be
π∗
=
µ
σ2γ

 1
1 + θ

1
γ
− 1


 . (17)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 21 / 40
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
2
4
6
8
10
Figure 3: Optimal investment strategy versus θ and γ with the parameters µ = 0.2, σ = 0.2 in
the homogeneous agents case for a single stock.
Note that for θ = 0.75 and 1
γ
= 2 both in Figure 3 and the right picture of Figure 1,
the optimal π∗
value is found as 5.7143.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 22 / 40
Corollary
If the agents are homogeneous in their preferences, the optimal strategy of the
representative agent is given as different depending on the boundary values of the
influence constant θ.
(i) When the group Y has no influence on the agent X, that is θ = 0, we have
π∗
=
µ
σ2γ
providing us to make a comparison with (9), which is also the result under the pure
jump diffusion case for the group.
(ii) If the group Y has full impact on the agent X, that is θ = 1, (17) returns to be
π∗
=
µ
σ2
.
In this case, we observe that there is neither risk-aversion of the group nor the agent
on the optimal strategy.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 23 / 40
1 The pure jump case (σ = ν = 0):
We consider an assumption such that the diffusion constant parameters are equal to
zero to isolate the optimal strategy π∗
by (11).
No individual jump risk:
We consider the case where there is no individual jump risk, i.e., ε̃ = 0.
Hence, (11) reduces to
µ − λ(1 − πε)−γ
ε(1 − π̂ε̂)−θ(1−γ)
= 0.
Hence, we obtain the strategy as
π∗
=
1
ε
−
µ
λ
− 1
γ (1 − π̂ε̂)
θ

1− 1
γ

ε

1− 1
γ
 . (18)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 24 / 40
Single stock case:
Lemma
Assume that µ̂ = µ and ε = ε̂. Then, the optimal strategy without an individual jump
risk reads as
π̂ = E

1
ε
−
µ
λ
− 1
γ (1 − π̂ε)
θ

1− 1
γ

ε

1− 1
γ


 . (19)
Proof.
With the assumptions of µ̂ = µ and ε = ε̂ and averaging both sides, we obtain (19).
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 25 / 40
Homogeneous agents case:
We assume that the agents are homogeneous in the single stock.
Then, the strategy (19) returns to be
π∗
=
1
ε
−
µ
λ
− 1
γ (1 − π∗
ε)
θ

1− 1
γ

ε

1− 1
γ
 (20)
for a group of homogeneous agents where the average over agents disappears and
π∗
= π̂.
By some direct calculations in (20), we isolate π as
π∗
=
1
ε
−

λε
µ
 1
γ
1
1+θ( 1
γ
−1)
!
ε
. (21)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 26 / 40
Corollary
The optimal strategy (21) receives distinct values on the boundary values of θ.
(i) When the group performance does not affect the agent’s performance, that is θ = 0,
the optimal strategy is given by
π∗
=
1
ε
−

λε
µ
 1
γ
ε
.
(ii) When the agent’s performance is completely dependent on the group’s performance,
that is θ = 1, the optimal strategy is found as
π∗
=
1
ε
−
λ
µ
.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 27 / 40
Parameter choice for the numerical illustrations:
Now, we display the optimal strategies under this case. The wealth process X of the
agent have the same expected return and uncertainty in terms of the local variance
as in the pure diffusion case. Then, we have the following two equations with three
unknowns:
µ − ελ = 0.2
ε2
λ = 0.04.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 28 / 40
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
0.25
0.50
0.75
1.00
1.25
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
1
2
3
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
1
2
3
4
5
6
Figure 4: Optimal strategies versus θ and 1
γ
for µ = {0.263245, 0.4, 0.83245}, λ = {0.1, 1, 10},
ε = {0.63245, 0.2, 0.063245} in a pure jump model with downward jumps when ε̃ = 0.
The parameter λ is the frequency of the crashes in the market.
The larger the jumps, the more asymmetric return becomes.
When λ → ∞, ε → 0 and so that the optimal strategy approaches to the strategy
obtained by (17) in the pure diffusion case of the homogeneous agents.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 29 / 40
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
20
40
60
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
5
10
15
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
2
4
6
8
10
12
Figure 5: Optimal strategies versus θ and 1
γ
for µ = {−0.08284, −0.43245, −1.0648},
λ = {2, 10, 40}, ε = {−0.14142, −0.063245, −0.03162} in a pure jump model with upward
jumps when ε̃ = 0.
When λ gets larger, π∗
converges to the pure-diffusion case.
The model produces negative ε and positive µ values when λ = 0.1 which results in
no solution.
When λ = 1, then we find that µ = 0 under the zero interest rate assumption.
Then, there is an opportunity to win when there are stocks.
Therefore, when λ ≤ 1, the model contains arbitrage and the portfolio optimization
problem has no solution.
The investor gets a positive return on the stock, which creates even more arbitrage
between the jumps because she borrows the money in the bank, buys stocks and
earns an extra return µ, larger than 0.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 30 / 40
Homogeneous jump sizes:
When ε = ε̃, the jump sizes become homogeneous..
In this case, (11) deduces to
µ − λ(1 − πε)−γ
ε(1 − π̂ε̂)−θ(1−γ)
− λ̃(1 − πε)−γ
ε = 0.
Thus, the optimal strategy reads as
π∗
=
1
ε
−
µ
(λ(1−π̂ε̂)−θ(1−γ)+λ̃)ε
!− 1
γ
ε
. (22)
Lemma
(Single stock case) Assume that µ̂ = µ, ε = ε̃ = ε̂ and λ = λ̃. Then, the optimal
strategy can be obtained as
π̂ = E







1
ε
−
1 − µ
λε((1−π̂ε)−θ(1−γ)+1)
!− 1
γ
ε







(23)
where we also take the average of both sides.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 31 / 40
Homogeneous agents case:
In this case, the strategy is
π∗
=
1
ε
−
1 − µ
λε((1−π∗ε)−θ(1−γ)+1)
!− 1
γ
ε
. (24)
By some straightforward calculations, we have
µ
λε
(1 − π∗
ε)γ
− (1 − π∗
ε)−θ(1−γ)
= 1. (25)
Corollary
When θ = 0 in (25), the optimal strategy π is given by
π∗
=
1
ε
−
µ
2λε
− 1
γ
ε
. (26)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 32 / 40
Independent individual jump risk:
When ε = 0 in (1), there is no correlation between the agent and the group.
In this case, (11) turns out to be
µ − λ̃(1 − πε̃)−γ
ε̃ = 0.
Then, the optimal strategy is obtained as
π∗
=
1 −

µ
λ̃ε̃
− 1
γ
ε̃
. (27)
Remark
When σ = 0 and ε = 0, we have a jump-diffusion case but we do not have joint risk
between the agent and the group. Therefore, θ disappears in the optimal strategy
formula, e.g. in (27), since it does not matter in this case. θ only appears together with
joint risk, that is, when σ = σ̂  0 or ε = ε̂  0.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 32 / 40
Remark
When the agent does not care about the group’s performance, that is when θ = 0, the
risk-aversion degree of the agent, which is γ, always appears on the optimal strategy
formula. This result makes sense because the degree of the risk aversion of the agent
determines the strategy playing an important role. When θ = 1, no γ appears on the
formulas.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 33 / 40
Benchmark portfolios:
Small benchmark portfolio without individual jump risk:
In this case, we insert (10) into (18) to get
π∗
=
1
ε
−
µ
λ
− 1
γ
µ̂
λε̂
 θ
η

1
γ
−1

ε

1− 1
γ
 . (28)
Lemma
(Single stock) Assume that µ̂ = µ and ε = ε̂. Then, the optimal strategy for a small
benchmark portfolio can be found as
π∗
=
1
ε
−
µ
λ
− 1
γ

ε
 µ
λε
 θ
η


1
γ
−1

. (29)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 34 / 40
Benchmark portfolios:
Market benchmark portfolio without individual jump risk:
We obtain the optimal strategy of the agent for a jump-diffusion model under the
same case in a market benchmark portfolio, plugging π̂ = 1 into the strategy (18).
Lemma
(Single stock) Assume that µ̂ = µ, ε = ε̂ and all agents are homogeneous. Then, the
optimal strategy for a market benchmark portfolio is found as
π∗
=
1
ε
−
µ
λ
− 1
γ (1 − ε)
θ

1− 1
γ

ε

1− 1
γ
 . (30)
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 35 / 40
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
0.25
0.50
0.75
1.00
1.25
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
0.25
0.50
0.75
1.00
1.25
(a) Optimal equilibrium strategy (left picture) and market benchmark portfolio strategy (right picture)
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
0.25
0.50
0.75
1.00
1.25
1
γ
0.0
0.5
1.0
1.5
2.0
θ
0.0
0.2
0.4
0.6
0.8
1.0
π
0.25
0.50
0.75
1.00
1.25
(b) Small benchmark portfolio strategy when η = 1.1 (left picture) and η = 2 (right picture), respectively
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 36 / 40
Concluding Remarks
We considered optimal portfolio investment strategies with CRRA utility function in
a jump-diffusion market under the relative performance concerns.
We found the results for one agent influenced by the group’s decisions.
We simplified the models in Lacker and Zariphopoulou [7] considering one agent and
a group of agents and also recovered their results when n → ∞ in their models for
the pure-diffusion case.
We found that the influence of the group affects the decision of the agent in
combination with the degree of risk-aversion.
We discovered that the number of the crashes in the market also affect the agent’s
strategy and even creates an arbitrage.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 37 / 40
Bibliography I
S. Basak and D. Makarov, Competition among portfolio managers and asset
specialization, https://ssrn.com/abstract=1563567, 2015.
N. Bäuerle and T. Göll, Nash equilibria for relative investors with (non)linear price
impact, arXiv:2303.18161, 2023.
P. DeMarzo, R. Kaniel, and I. Kremer, Relative wealth concerns and financial
bubbles, Review of Financial Studies, 21(1), pp. 19–50, 2008.
G. E. Espinosa and N. Touzi, Optimal investment under relative performance
concerns, Mathematical Finance, 25(2), pp. 221–257, 2015.
J. Gali, Keeping up with the joneses: Consumption externalities, portfolio choice and
asset pricess, Journal of Money Credit Banking, 26, pp. 1–8, 1994.
D. Lacker and A. Soret, Many-player games of optimal consumption and investment
under relative performance criteria, Mathematics and Financial Economics, 14, pp.
263–281, 2020.
D. Lacker and T. Zariphopoulou, Mean-field and n-agent games for optimal
investment under relative performance criteria, Mathematical Finance, 29, pp.
1003–1038, 2019.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 38 / 40
Bibliography II
G. D. Reis and V. Platonov, Forward utilities and mean-field games under relative
performance concerns, Paper presented at the International Conference, Particle
Systems and PDEs VI, VII and VIII, 2021.
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 39 / 40
THANK YOU FOR YOUR ATTENTION!
B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets
June 26, 2023 40 / 40

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  • 1. Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets 22nd ECMI Conference on Industrial and Applied Mathematics, 26-30 June 2023 - Wroclaw, Poland Burcu Aydoğan (Joint work with Mogens Steffensen in the University of Copenhagen) RWTH Aachen University June 26, 2023 B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 1 / 40
  • 2. Outline 1 Introduction 2 Framework 3 Concluding Remarks B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 2 / 40
  • 3. Introduction Our problem: Determine the optimal investment strategies of one agent and (a large group of agents) having CRRA utilities under relative performance concerns. There is a strategic interaction between the agent and the group which is caused by their relative performances. We solve two classical Merton problems to determine what the group does and the agent’s optimal strategy relative to the group’s performance. There are some studies which revealed the significance of the relative performance concerns on human behaviors, see for instance [3] and [5]. In our framework, the stock price is defined on jump-diffusion markets where we both consider the upward and downward jumps in the numerical observations. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 3 / 40
  • 4. Basak and Makarov [1] work on a portfolio choice problem with a competition between two risk-averse portfolio managers where the stock follows geometric Brownian motion. Espinosa and Touzi [4] consider n interacting agents maximizing the difference between an agent’s wealth and average wealth of other agents’ wealth. Lacker and Zariphopoulou [7] work on an optimal portfolio management problem for interacting n interacting agents with both CARA and CRRA utilities. They obtain equilibrium strategies for both n agents and mean-field games. Lacker and Soret [6] extend the CRRA model developed by Lacker and Zariphopoulou [7] for a continuous time-dependent problem including relative performances. Reis and Platonov [8] develop equilibrium strategies using forward utilities of CARA type. Bäuerle and Göll [2] obtain Nash equilibrium investment strategies under the strategic interactions of n agents investigating the influence of the price impact on the equilibrium. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 4 / 40
  • 5. Our work is a special case of the paper Lacker and Zariphopoulou [7] in the following directions: (i) We simplify their mean-field equilibrium results by considering only one agent and a group of agents. (ii) In our framework, the stock price is followed in a jump-diffusion market as follows: dSt = St µdt + νdWt + σdBt − εdNt − ε̃dÑt with constant parameters µ, ν, σ 0; the constant jump sizes ε, ε̃; two independent standard Brownian motions Wt and Bt and two independent Poisson processes Nt and Ñt. (iii) Moreover, we assume that the agents in the market are homogeneous in their risk-aversions and relative performances as a special case. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 5 / 40
  • 6. Framework We define a complete probability space (Ω, F, P) with a sample space Ω, a filtration F = {Ft}0≤t≤T and a probability measure P. The agent and the group trade using self-financing strategies πt and π̂t which represent the optimal proportional allocations in the portfolio, respectively. Let X and Y denote the wealth of the agent and the group. We suppose that they are generated by the dynamics, dXt = πtXt µdt + νdWt + σdBt − εdNt − ε̃dÑt , X0 = x0; dYt = π̂tYt µ̂dt + σ̂dBt − ε̂dNt , Y0 = y0. (1) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 6 / 40
  • 7. In this setup, (i) µ, µ̂ are the constant drift parameters; (ii) ν, σ, σ̂ 0 are the constant volatility parameters; (iii) Wt and Bt are independent standard Brownian motions; W is an idiosyncratic noise and B is the common noise; (iv) ε, ε̃, ε̂ are the constant jump sizes; (v) Nt and Ñt are two independent Poisson processes with the constant intensities λ and λ̃, respectively; (vi) the allocations π and π̂ determine the proportion of the agent’s wealth and the group’s wealth, respectively. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 7 / 40
  • 8. Optimal control problem for the group The utility function of the group: V (Y ) = 1 1 − η Y 1−η where η 0, η ̸= 1 is the risk-aversion of the group. The optimization problem of the group: u(y, t) = sup π̂∈ E[V (Y )] = sup π̂∈ E[V (y) | Y0 = y] (2) where  is the set of admissible strategies which is defined as  = π̂ : π̂t ∈ Ft, E Z T 0 |π̂t|2 dt ∞ and Yt 0, t 0 . B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 8 / 40
  • 9. The Hamilton-Jacobi-Bellman (HJB) equation for the value function (2): ut + sup π̂∈A µ̂π̂ yuy + 1 2 σ̂2 π̂2 y2 uyy + λ u(y − π̂yε̂, t) − u(y, t) = 0 (3) for (y, t) ∈ R+ × [0, T] with the terminal condition u(y, T) = 1 1 − η y1−η . The resulting equation for π̂: µ̂ − σ̂2 π̂η − λε̂(1 − π̂ε̂)−η = 0. (4) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 9 / 40
  • 10. Optimal control problem for the agent The utility function of the agent: U(X, Y ) = 1 1 − γ XY −θ 1−γ (5) where γ 0, γ ̸= 1 is the risk-aversion of the agent and 0 ≤ θ ≤ 1 specifies the influence from the group Y on the utility of the agent. Some comments on the utility function: When θ = 0, the group’s performance does not impact the agent’s performance. When θ = 1, the utility function (5) is U(X, Y ) = 1 1 − γ X Y 1−γ , such that the utility is gained from a direct relative performance between the agent and the group. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 10 / 40
  • 11. The stochastic optimal control problem of the agent: w(x, y, t) = sup π∈A E [U(X(T), Y (T)) | X0 = x, Y0 = y] = sup π∈A E 1 1 − γ X(T)Y −θ (T) 1−γ | X0 = x, Y0 = y , (6) where A is the set of admissible strategies for the optimal strategies π which is given as A = π : πt ∈ Ft, E Z T 0 |πt|2 dt ∞ and Yt 0, t 0 . The Hamilton-Jacobi-Bellman (HJB) equation: 0 =wt + µ̂yπ̂wy + 1 2 σ̂2 y2 π̂2 wyy + sup π∈A π (µxwx + σσ̂xyπ̂wxy) + 1 2 v2 + σ2 π2 x2 wxx + λ w(x − πxε, y − π̂yε̂, t) − w(x, y, t) + λ̃ w(x − πxε̃, y, t) − w(x, y, t) o (7) for (x, y, t) ∈ R+ × R+ × [0, T] with the final condition w(x, y, T) = 1 1 − γ xy−θ 1−γ . B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 11 / 40
  • 12. The ansatz w(x, y, t) = g(t) 1 1−γ xy−θ 1−γ yields the ODE g′ (t) + ρ̃g(t) = 0 where ρ̃ = −µ̂π̂θ(1 − γ) − 1 2 σ̂2 π̂2 θ(θγ − θ − 1)(1 − γ) + sup π∈A µπ(1 − γ) − σσ̂π̂θ(1 − γ)2 π − 1 2 (ν2 + σ2 )π2 γ(1 − γ) +λ (1 − πε)(1 − π̂ε̂)−θ 1−γ − 1 + λ̃ (1 − πε̃)1−γ − 1 . The resulting equation for π: µ − σσ̂π̂θ(1 − γ) − (ν2 + σ2 )πγ − λ(1 − πε)−γ ε(1 − π̂ϵ̂)−θ(1−γ) − λ̃(1 − πε̃)−γ ε̃ = 0. (8) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 12 / 40
  • 13. Optimal strategies of the group: Remember that the resulting equation for π̂ is µ̂ − σ̂2 π̂η − λε̂(1 − π̂ε̂)−η = 0. The pure diffusion case (ε̂ = 0): π̂∗ = µ̂ σ̂2η , (9) which is the classical Merton optimal strategy. The pure jump case (σ̂ = 0): π̂∗ = 1 ε̂ − ( µ̂ λε̂ ) − 1 η ε̂ . (10) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 13 / 40
  • 14. Optimal strategies of the agent: Remember that the resulting equation for π is µ − σσ̂π̂θ(1 − γ) − (ν2 + σ2 )πγ − λ(1 − πε)−γ ε(1 − π̂ϵ̂)−θ(1−γ) − λ̃(1 − πε̃)−γ ε̃ = 0. (11) 1 The pure diffusion case (ε = ε̃ = 0): π∗ = 1 γ µ − σσ̂π̂θ( 1 γ − 1) v2 + σ2 (12) where 1 γ is defined as the risk-tolerance parameter of the agent. We discuss this result in relation to certain results achieved by Lacker and Zariphopoulou [7] where they obtain a Mean Field Equilibrium strategy under relative performances. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 14 / 40
  • 15. Lemma Assuming that the agent has the optimal strategy π given by (12), we recover the Mean Field Equilibrium strategy in Lacker and Zariphopoulou [7]. Proof. The Mean Field Equilibrium strategy formula in Lacker and Zariphopoulou [7] reads π∗ = δ · µ σ2 + v2 − θ(δ − 1) σ σ2 + v2 · φ 1 + ψ , where the constants φ and ψ are defined as φ := E δ µσ σ2 + ν2 # and ψ := E θ(δ − 1) σ2 σ2 + ν2 # , the expectations are essentially averages over individuals in their mean-field approach and δ = 1/γ. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 15 / 40
  • 16. Proof (Cont.) The task is to develop the mean-field version of σ̂π̂. Multiply both sides of (12) by σ to obtain σπ∗ = 1 γ µσ v2 + σ2 − σ2 σ̂π̂θ( 1 γ − 1) v2 + σ2 . (13) Now, take the average over all individuals on both sides and denote the average over individuals as a plain expectation. Then, the left-hand side becomes σ̂π̂ = E[σπ∗ ], and the right-hand side becomes E 1 γ µσ v2 + σ2 # − E σ2 σ̂π̂θ( 1 γ − 1) v2 + σ2 # = ψ + σ̂π̂φ. Equating the two sides and solving for σ̂π̂ gives σ̂π̂ = ψ 1 + φ . (14) Plugging (14) back into (12) gives exactly the Mean Field Equilibrium strategy in Lacker and Zariphopoulou [7]. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 16 / 40
  • 17. Single stock case: Lemma Assume that µ̂ = µ, σ̂ = σ and v = 0. Then, the optimal strategy reads as π∗ = µ σ2   1 γ − E h 1 γ i 1 + E h θ 1 γ − 1 iθ 1 γ − 1   . (15) Proof. When µ̂ = µ, σ̂ = σ and v = 0, (12) simplifies to π∗ = 1 γ µ σ2 − π̂θ 1 γ − 1 . (16) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 17 / 40
  • 18. Proof (Cont.) Averaging over both sides gives π̂ = E 1 γ µ σ2 − π̂E θ 1 γ − 1 . Solved for π̂ gives π̂ = E h 1 γ i µ σ2 1 + E h θ 1 γ − 1 i. Then, plugged into π∗ in (16) gives us (15). B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 18 / 40
  • 19. δ 0.0 0.5 1.0 1.5 2.0 ̄ θ 0.0 0.2 0.4 0.6 0.8 1.0 π 3 4 5 6 7 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 2 4 6 8 10 Figure 1: (Single stock case) Optimal strategy π∗ versus θ̄ = E[θ] and δ = 1 γ in Lacker and Zariphopoulou [7] with θ = 3 4 and δ̄ = E h 1 γ i = 2 and our strategy π∗ in (15) versus θ and 1 γ with E[θ] = 3 4 and E h 1 γ i = 2 with the common parameters µ = 5, σ = 1. Note that we assume θ and 1 γ are uncorrelated to generate the above results. When θ = 0, then π∗ increases linearly. When θ = 1, π∗ is independent of γ. When γ 1, π∗ increases in θ. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 19 / 40
  • 20. 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 δ = 1 γ 2 3 4 5 6 7 8 π theta1=0.25 theta2=0.6 theta3=0.9 Figure 2: Optimal investment strategy versus δ = 1 γ for different θ values. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 20 / 40
  • 21. Homogeneous agents case: The agents are homogeneous in their risk-aversions and relative performances, i.e. E h 1 γ i = 1 γ and E[θ] = θ. By this assumption, (15) turns out to be π∗ = µ σ2γ   1 1 + θ 1 γ − 1   . (17) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 21 / 40
  • 22. 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 2 4 6 8 10 Figure 3: Optimal investment strategy versus θ and γ with the parameters µ = 0.2, σ = 0.2 in the homogeneous agents case for a single stock. Note that for θ = 0.75 and 1 γ = 2 both in Figure 3 and the right picture of Figure 1, the optimal π∗ value is found as 5.7143. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 22 / 40
  • 23. Corollary If the agents are homogeneous in their preferences, the optimal strategy of the representative agent is given as different depending on the boundary values of the influence constant θ. (i) When the group Y has no influence on the agent X, that is θ = 0, we have π∗ = µ σ2γ providing us to make a comparison with (9), which is also the result under the pure jump diffusion case for the group. (ii) If the group Y has full impact on the agent X, that is θ = 1, (17) returns to be π∗ = µ σ2 . In this case, we observe that there is neither risk-aversion of the group nor the agent on the optimal strategy. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 23 / 40
  • 24. 1 The pure jump case (σ = ν = 0): We consider an assumption such that the diffusion constant parameters are equal to zero to isolate the optimal strategy π∗ by (11). No individual jump risk: We consider the case where there is no individual jump risk, i.e., ε̃ = 0. Hence, (11) reduces to µ − λ(1 − πε)−γ ε(1 − π̂ε̂)−θ(1−γ) = 0. Hence, we obtain the strategy as π∗ = 1 ε − µ λ − 1 γ (1 − π̂ε̂) θ 1− 1 γ ε 1− 1 γ . (18) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 24 / 40
  • 25. Single stock case: Lemma Assume that µ̂ = µ and ε = ε̂. Then, the optimal strategy without an individual jump risk reads as π̂ = E  1 ε − µ λ − 1 γ (1 − π̂ε) θ 1− 1 γ ε 1− 1 γ   . (19) Proof. With the assumptions of µ̂ = µ and ε = ε̂ and averaging both sides, we obtain (19). B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 25 / 40
  • 26. Homogeneous agents case: We assume that the agents are homogeneous in the single stock. Then, the strategy (19) returns to be π∗ = 1 ε − µ λ − 1 γ (1 − π∗ ε) θ 1− 1 γ ε 1− 1 γ (20) for a group of homogeneous agents where the average over agents disappears and π∗ = π̂. By some direct calculations in (20), we isolate π as π∗ = 1 ε − λε µ 1 γ 1 1+θ( 1 γ −1) ! ε . (21) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 26 / 40
  • 27. Corollary The optimal strategy (21) receives distinct values on the boundary values of θ. (i) When the group performance does not affect the agent’s performance, that is θ = 0, the optimal strategy is given by π∗ = 1 ε − λε µ 1 γ ε . (ii) When the agent’s performance is completely dependent on the group’s performance, that is θ = 1, the optimal strategy is found as π∗ = 1 ε − λ µ . B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 27 / 40
  • 28. Parameter choice for the numerical illustrations: Now, we display the optimal strategies under this case. The wealth process X of the agent have the same expected return and uncertainty in terms of the local variance as in the pure diffusion case. Then, we have the following two equations with three unknowns: µ − ελ = 0.2 ε2 λ = 0.04. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 28 / 40
  • 29. 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 0.25 0.50 0.75 1.00 1.25 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 1 2 3 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 1 2 3 4 5 6 Figure 4: Optimal strategies versus θ and 1 γ for µ = {0.263245, 0.4, 0.83245}, λ = {0.1, 1, 10}, ε = {0.63245, 0.2, 0.063245} in a pure jump model with downward jumps when ε̃ = 0. The parameter λ is the frequency of the crashes in the market. The larger the jumps, the more asymmetric return becomes. When λ → ∞, ε → 0 and so that the optimal strategy approaches to the strategy obtained by (17) in the pure diffusion case of the homogeneous agents. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 29 / 40
  • 30. 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 20 40 60 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 5 10 15 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 2 4 6 8 10 12 Figure 5: Optimal strategies versus θ and 1 γ for µ = {−0.08284, −0.43245, −1.0648}, λ = {2, 10, 40}, ε = {−0.14142, −0.063245, −0.03162} in a pure jump model with upward jumps when ε̃ = 0. When λ gets larger, π∗ converges to the pure-diffusion case. The model produces negative ε and positive µ values when λ = 0.1 which results in no solution. When λ = 1, then we find that µ = 0 under the zero interest rate assumption. Then, there is an opportunity to win when there are stocks. Therefore, when λ ≤ 1, the model contains arbitrage and the portfolio optimization problem has no solution. The investor gets a positive return on the stock, which creates even more arbitrage between the jumps because she borrows the money in the bank, buys stocks and earns an extra return µ, larger than 0. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 30 / 40
  • 31. Homogeneous jump sizes: When ε = ε̃, the jump sizes become homogeneous.. In this case, (11) deduces to µ − λ(1 − πε)−γ ε(1 − π̂ε̂)−θ(1−γ) − λ̃(1 − πε)−γ ε = 0. Thus, the optimal strategy reads as π∗ = 1 ε − µ (λ(1−π̂ε̂)−θ(1−γ)+λ̃)ε !− 1 γ ε . (22) Lemma (Single stock case) Assume that µ̂ = µ, ε = ε̃ = ε̂ and λ = λ̃. Then, the optimal strategy can be obtained as π̂ = E        1 ε − 1 − µ λε((1−π̂ε)−θ(1−γ)+1) !− 1 γ ε        (23) where we also take the average of both sides. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 31 / 40
  • 32. Homogeneous agents case: In this case, the strategy is π∗ = 1 ε − 1 − µ λε((1−π∗ε)−θ(1−γ)+1) !− 1 γ ε . (24) By some straightforward calculations, we have µ λε (1 − π∗ ε)γ − (1 − π∗ ε)−θ(1−γ) = 1. (25) Corollary When θ = 0 in (25), the optimal strategy π is given by π∗ = 1 ε − µ 2λε − 1 γ ε . (26) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 32 / 40
  • 33. Independent individual jump risk: When ε = 0 in (1), there is no correlation between the agent and the group. In this case, (11) turns out to be µ − λ̃(1 − πε̃)−γ ε̃ = 0. Then, the optimal strategy is obtained as π∗ = 1 − µ λ̃ε̃ − 1 γ ε̃ . (27) Remark When σ = 0 and ε = 0, we have a jump-diffusion case but we do not have joint risk between the agent and the group. Therefore, θ disappears in the optimal strategy formula, e.g. in (27), since it does not matter in this case. θ only appears together with joint risk, that is, when σ = σ̂ 0 or ε = ε̂ 0. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 32 / 40
  • 34. Remark When the agent does not care about the group’s performance, that is when θ = 0, the risk-aversion degree of the agent, which is γ, always appears on the optimal strategy formula. This result makes sense because the degree of the risk aversion of the agent determines the strategy playing an important role. When θ = 1, no γ appears on the formulas. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 33 / 40
  • 35. Benchmark portfolios: Small benchmark portfolio without individual jump risk: In this case, we insert (10) into (18) to get π∗ = 1 ε − µ λ − 1 γ µ̂ λε̂ θ η 1 γ −1 ε 1− 1 γ . (28) Lemma (Single stock) Assume that µ̂ = µ and ε = ε̂. Then, the optimal strategy for a small benchmark portfolio can be found as π∗ = 1 ε − µ λ − 1 γ ε µ λε θ η 1 γ −1 . (29) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 34 / 40
  • 36. Benchmark portfolios: Market benchmark portfolio without individual jump risk: We obtain the optimal strategy of the agent for a jump-diffusion model under the same case in a market benchmark portfolio, plugging π̂ = 1 into the strategy (18). Lemma (Single stock) Assume that µ̂ = µ, ε = ε̂ and all agents are homogeneous. Then, the optimal strategy for a market benchmark portfolio is found as π∗ = 1 ε − µ λ − 1 γ (1 − ε) θ 1− 1 γ ε 1− 1 γ . (30) B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 35 / 40
  • 37. 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 0.25 0.50 0.75 1.00 1.25 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 0.25 0.50 0.75 1.00 1.25 (a) Optimal equilibrium strategy (left picture) and market benchmark portfolio strategy (right picture) 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 0.25 0.50 0.75 1.00 1.25 1 γ 0.0 0.5 1.0 1.5 2.0 θ 0.0 0.2 0.4 0.6 0.8 1.0 π 0.25 0.50 0.75 1.00 1.25 (b) Small benchmark portfolio strategy when η = 1.1 (left picture) and η = 2 (right picture), respectively B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 36 / 40
  • 38. Concluding Remarks We considered optimal portfolio investment strategies with CRRA utility function in a jump-diffusion market under the relative performance concerns. We found the results for one agent influenced by the group’s decisions. We simplified the models in Lacker and Zariphopoulou [7] considering one agent and a group of agents and also recovered their results when n → ∞ in their models for the pure-diffusion case. We found that the influence of the group affects the decision of the agent in combination with the degree of risk-aversion. We discovered that the number of the crashes in the market also affect the agent’s strategy and even creates an arbitrage. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 37 / 40
  • 39. Bibliography I S. Basak and D. Makarov, Competition among portfolio managers and asset specialization, https://ssrn.com/abstract=1563567, 2015. N. Bäuerle and T. Göll, Nash equilibria for relative investors with (non)linear price impact, arXiv:2303.18161, 2023. P. DeMarzo, R. Kaniel, and I. Kremer, Relative wealth concerns and financial bubbles, Review of Financial Studies, 21(1), pp. 19–50, 2008. G. E. Espinosa and N. Touzi, Optimal investment under relative performance concerns, Mathematical Finance, 25(2), pp. 221–257, 2015. J. Gali, Keeping up with the joneses: Consumption externalities, portfolio choice and asset pricess, Journal of Money Credit Banking, 26, pp. 1–8, 1994. D. Lacker and A. Soret, Many-player games of optimal consumption and investment under relative performance criteria, Mathematics and Financial Economics, 14, pp. 263–281, 2020. D. Lacker and T. Zariphopoulou, Mean-field and n-agent games for optimal investment under relative performance criteria, Mathematical Finance, 29, pp. 1003–1038, 2019. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 38 / 40
  • 40. Bibliography II G. D. Reis and V. Platonov, Forward utilities and mean-field games under relative performance concerns, Paper presented at the International Conference, Particle Systems and PDEs VI, VII and VIII, 2021. B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 39 / 40
  • 41. THANK YOU FOR YOUR ATTENTION! B. Aydoğan (RWTH Aachen University) Optimal Investment Strategies Under the Relative Performance in Jump-Diffusion Markets June 26, 2023 40 / 40