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International Journal of Business Marketing and Management (IJBMM)
Volume 8 Issue 2 Mar-Apr 2023, P.P. 91-101
ISSN: 2456-4559
www.ijbmm.com
International Journal of Business Marketing and Management (IJBMM) Page 91
Robust Optimal Reinsurance and Investment Problem
with p-Thinning Dependent and Default risks
Yingqi Liang1
, Peibiao Zhao1
1
School of Mathematics and Statistics,Nanjing University of Science and Technology, Nanjing Jiangsu
210094,China
843186823@
Abstract: In this paper, we consider an AAI with two types of insurance business with p-thinning dependent
claims risk, diversify claims risk by purchasing proportional reinsurance, and invest in a stock with Heston
model price process, a risk-free bond, and a credit bond in the financial market with the objective of maximizing
the expectation of the terminal wealth index effect, and construct the wealth process of AAI as well as the the
model of robust optimal reinsurance-investment problem is obtained, using dynamic programming, the HJB
equation to obtain the pre-default and post-default reinsurance-investment strategies and the display expression
of the value function, respectively, and the sensitivity of the model parameters is analyzed through numerical
experiments to obtain a realistic economic interpretation. The model as well as the results in this paper are a
generalization and extension of the results of existing studies.
Key words: p-Thinning dependent risk, defaultable bonds, dynamic programming, HJB equation, robust
optimization.
I. Introduction
The sound operation and solid claiming ability of insurance companies are important to maintain social
stability and promote social development, and the purchase of reinsurance can well control the risk of insurance
companies. The current research on reinsurance in the actuarial field of insurance mainly focuses on the insurer's
objective function, investment type, claim process, and price process of assets. [1]-[3]studied the most available
reinsurance investment problems under different utility function. [4]-[7]investigate the optimal reinsurance
investment problem under different risky asset price process.
Most of the current literature considers only single-risk claims, while in reality the risks are usually
correlated with each other. The current literature on claim dependency risk is divided into two main types of
dependency, one is co-impact and the other is p-thinning dependency. P-thinning dependency means that when
one type of claim occurs, there is a certain probability p that another type of claim will occur, for example, a car
accident or fire will not only cause property damage, but also loss of life if the situation is serious. The problem
under diffusion approximation model, jump diffusion risk model is studied in[8][9],[10] studied the type of
dependent risk for common shocks, and [11] considered the risk process under p-thinning dependence. Most of
the current studies consider only two assets for considering investments in credit bonds. [12]-[14] take into
account defaulted bonds among the types of investments for insurers. Since models with diffusion and jump
terms usually introduce uncertainty in the model for insurers, insurers usually want to seek a more robust model.
[15]-[17] study the AAI most reinsurance-investment problem.
Based on this, this paper studies the optimal proportional reinsurance-investment problem of AAI under the
Heston model by considering both sparse dependence and claims risk based on [11][14][17]. The paper is
organized as follows: a robust optimal reinsurance-investment problem model under p-thinning dependence and
default risk is developed in Section 2. The value function is divided into pre-default and post-default in Section
3, and the optimal reinsurance-investment strategies are solved for pre-default and post-default using dynamic
programming, optimal control theory, and the HJB equation, respectively. Parameter sensitivities are analyzed,
and economic explanations are given in Section 4. Section 5 concludes the paper.
II. Model Formulation
Suppose *Ω, F, *ð¹ð‘¡+t∈,0,T -, P+ is a complete probability space, the positive number T denotes the final
value moment, [0, T ] is a fixed time interval, ð¹ð‘¡ denotes the information in the market up to time t, and 𔽠∶=
*ð¹ð‘¡+t∈,0,T -denotes the standard Brownian motion ð‘Š0(ð‘¡), ð‘Š1(ð‘¡), ð‘Š2(ð‘¡), ð‘Š3(ð‘¡). Poisson process N(t), and the
right-continuous P-complete information flow generated by the sequence of random variables *ð‘‹ð‘–, 𑖠≥ 1+,
*ð‘Œð‘–, 𑖠≥ 1+. ℠∶= (â„‹ð‘¡)t⩾0 is the information flow generated by the violation process H(t), let ð”¾: = (ð’¢ð‘¡)t⩾0, be
the information flow generated by ð”½, â„ the expanded information flow, i.e., ð”¾: = ℱ𑡠∨ â„‹ð‘¡. By definition, each
𔽠-harness is also the 𔾠-harness. The probability measure P is a realistic probability measure and Q is a risk-
neutral measure. In addition, it is assumed that all transactions in the financial market are continuous, and no
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 92
taxes do not incur transaction costs and all property is infinitely divisible.
1.1 Surplus Process
Assuming that the insurer operates two different lines of business and that there is a sparse dependency between
these two lines of business, the surplus process is as follows:
R(t) = ð‘¥0 + ð‘𑡠− (∑ ð‘‹ð‘–
ð‘(ð‘¡)
ð‘–=1
+ ∑ ð‘Œð‘–
ð‘ð‘(ð‘¡)
ð‘–=1
) . #(1)
where{ð‘‹ð‘–,𑖠≥ 1} is independently and identically distributed in ð¹ð‘‹(∙),ð¸(ð‘‹) = ðœ‡ð‘‹ > 0,ð¸(ð‘‹2
) = ðœð‘‹
2
, as the
claim amount of the first class of business,{ð‘Œð‘–,𑖠≥ 1} is independently and identically distributed inð¹ð‘Œ(∙
),ð¸(ð‘Œ) = ðœ‡ð‘Œ > 0,ð¸(ð‘Œ2
) = ðœð‘Œ
2
, as the claim amount of the second class of business. the claim amount of the
second type of business. N(t)denotes the conforming Poisson process with parameter c denotes the premium of
the insurance company by the expected value premium there are c = (1 + θ1)λðœ‡ð‘‹ + (1 + θ2)λpðœ‡ð‘Œ.θ1 > 0,θ2 >
0.
1.2 Proportional Reinsurance
Assuming that the insurer diversifies the claim risk by purchasing proportional reinsurance, and let ð‘ž1(ð‘¡),ð‘ž2(ð‘¡)
be the insurer's retention ratio, the claim after the insurer purchases reinsurance is:
ð‘ž1(ð‘¡)ð‘‹ð‘– , ð‘ž2(ð‘¡)ð‘Œð‘– then the reinsurance fee is δ(ð‘ž1(ð‘¡), ð‘ž2(ð‘¡)) = (1 + η1)(1 − ð‘ž1(ð‘¡))λðœ‡ð‘‹ + (1 + η2)(1 −
ð‘ž2(ð‘¡))λpðœ‡ð‘Œ.According to Grandell(1991)[8]
,the claims process can be diffusely approximated as:
d ∑ Xi
N(t)
i=1
= λE(Xi)dt − γ1dWX(t), γ1 = √λE(XI
2
)
d ∑ Yi
Np(t)
i=1
= λE(Yi)dt − γ2dWY(t), γ2 = √λE(YI
2
)
The correlation coefficient of ð‘Šð‘‹(ð‘¡)ð‘Šð‘Œ(ð‘¡ )is Ï
Ì‚ =
λp
ð›¾1ð›¾2
E(ð‘‹ð‘–)E(ð‘Œð‘–).Then the wealth process of the insurer after
joining the reinsurance is:
dXq1,q2 = ,λμX(θ1 − η1 + η1ð‘ž1(ð‘¡)) + λpμY(θ2 − η2
+η2ð‘ž2(ð‘¡))ð‘‘ð‘¡ + √(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï
Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2dW0
1.3 Financial Market
Suppose the financial market consists of three assets: risk-free assets, stocks, and corporate bonds, and the price
processes of the three assets are as follows: The price process of risk-free bonds is given by:ð‘‘R(t) =
rR(t)dt.The stock price process S(t) obeys the Heston stochastic volatility model:
{
ð‘‘ð‘†(ð‘¡) = ð‘†(ð‘¡),ð‘Ÿ + ð›¼ð¿(ð‘¡)ð‘‘ð‘¡ + √ð¿(ð‘¡)ð‘‘ð‘Š1(ð‘¡)-, ð‘†(0) = ð‘ 0
ð‘‘ð¿(ð‘¡) = ð‘˜(𜔠− ð¿(ð‘¡))ð‘‘ð‘¡ + ðœâˆšð¿(ð‘¡)ð‘‘ð‘Š2(ð‘¡), ð¿(0) = ð‘™0
R is the risk-free rate,α, ð‘˜, Ï‚, are positive constant.ð¸,ð‘Š1ð‘Š2- = Ït, 2ð‘˜ðœ” ≥ Ï‚2
Following Bielecki (2007)[18]
, the credit bond price process p(t, T1), under a realistic measure P, using an
approximate model to portray default risk is as follows:
dp(t, T1) = p(t−, T1),(r + (1 − H(t))δ(1 − Δ)dt
−(1 − H(t−))ζdMp
(t)-
Where Mp
(t) = H(t) − hQ
∫ Δ(1 − H(u))du
t
0
is aâ„Š − harness, δ = ð‘•ð‘„
ζ is the credit spread.
1.4 Robust optimization problem
Assuming the insurer adopts a reinsurance investment strategyε(t) = (ð‘ž1(ð‘¡), ð‘ž2(ð‘¡), Ï€(t), β(ð‘¡)),ð‘ž1(ð‘¡), ð‘ž2(ð‘¡)are
the reinsurance strategies adopted by the insurer at moment t in the first and second asset classes,
respectively.Ï€(t) for the insurance company's investment in equities at time t.,β(ð‘¡)for the insurance company′s
investment in credit bonds at time t. Let 𔸠denotes the set of all feasible strategies, then the dynamic process of
wealth of the insurance company at this moment ð‘‹ðœ€
(t) is:
dð‘‹ðœ€(ð‘¡) = ðœ‹(ð‘¡)
ð‘‘ð‘†(ð‘¡)
ð‘†(ð‘¡)
+ β(ð‘¡)
ð‘‘ð‘(ð‘¡)
ð‘(ð‘¡)
+ (ð‘‹ðœ€(ð‘¡) − ðœ‹(ð‘¡) − β(ð‘¡))
ð‘‘ðµ(ð‘¡)
ðµ(ð‘¡)
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 93
+ð‘‘ð‘‹ð‘š(ð‘¡),Xε(0) = x0
Assume that the insurer maximizes the terminal T moment expected utility in the financial market, the portfolio
index utility, which takes the form of:
V(X(T)) = −
1
ð›¾
ð‘’−ð›¾ð‘‹(ð‘‡)
Where 𛾠> 0 is the ambiguity aversion coefficient of the insurer. The insurer's goal is to find the optimal
reinsurance-investment strategyðœ€âˆ—
(ð‘¡) = (ð‘ž1
∗
(ð‘¡), ð‘ž2
∗
(ð‘¡), ðœ‹âˆ—
(ð‘¡), β∗
(ð‘¡))to maximizing the expectation of end-use
wealth utility for insurers. The objective function of the insurer is:
Vε
(t, x, l, h) = E(u(Xε
(T))|Xε
(t) = x, L(t) = l)
The value function of the optimization problem is:
V(t, x, l, h) = Vε
(t, x, l, h)
ε∈Π
sup
, V(T,x,l,h)=v(x),
Assume that the ambiguity information is described by the probability P and the reference model is measured by
the probability ð’«Î¦
which is equivalent to P:ð’«: = *ð’«Î¦
|ð’«Î¦
~ð‘ƒ+.Next, the optional measure set is constructed,
defining the procedure :Φ(ð‘¡) = (Φ0(ð‘¡), Φ1(ð‘¡), Φ2(ð‘¡), Φ3(ð‘¡))s.t.:
1. Φ(ð‘¡) is a â„Š(ð‘¡)- measurable for any t[0,T]
2. Φi(t) = Φi(t, ω), i = 0,1,2,3 andΦi(t) ≥ 0 for all (t, ω) ∈ ,0, T- × Ω.
3.∫ ||Φ(t)||2
ð‘‘ð‘¡ < ∞;
ð‘‡
0
Let Σ be all processes shaped as Φ,for all Φ ∈ Σ define a G-adaptation process under a real measure
*ΛΦ
(ð‘¡)|𑡠∈ ,0, T-+.From Ito differentiation we have:
ð‘‘ΛΦ
(ð‘¡) = ΛΦ
(ð‘¡âˆ’)(−Φ0(ð‘¡)dW0 − Φ1(ð‘¡)ð‘‘ð‘Š1 − Φ2(ð‘¡)ð‘‘ð‘Š2 − (1 − Φ3(ð‘¡))ð‘‘Mp
)
Where ΛΦ
(0) = 1,P-a.s. ΛΦ
(ð‘¡) is a (P,G)- martingale,E[ΛΦ
(ð‘‡)] =1, for each Φ ∈ Σ,A new optional measure
is absolutely continuous to P, defined as
ð‘‘ð‘ƒÎ¦
ð‘‘ð‘ƒ
|ð’¢ð‘‡
= ΛΦ
(ð‘‡).
So far, we have constructed a class of real-world probability measures ð‘ƒÎ¦
,where Φ ∈ Σ,From Gisanova's
theorem[21]
,it follows that:
ð‘‘Wi
ð‘ƒÎ¦
(ð‘¡) = dWi(ð‘¡) + Φð‘–(ð‘¡)ð‘‘ð‘¡, ð‘– = 0,1,2
Therefore the wealth process in the ð‘ƒÎ¦
is:
dð‘‹ðœ€
(ð‘¡) = ,xr + ðœ‹(ð›¼ð‘™ − Φ1√ð‘™) + β(1 − H(t))δ(1 − Δ)
+λμX(θ1 − η1) + λpμY((θ2 − η2) + η1ð‘ž1(ð‘¡)) + η2ð‘ž2(ð‘¡))
+√(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï
Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2Φ0-dt + ðœ‹âˆšð‘™ð‘‘W1
ð‘ƒÎ¦
+β(1 − H(t−))ζdMp
+ √(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï
Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2ð‘‘W0
ð‘ƒÎ¦
(2)
We assume that the insurer determines a robust portfolio strategy such that the worst-case scenario is the best
option. The insurer penalizes any deviation from the sub-reference model with a penalty that increases with this
deviation, using relative entropy to measure the deviation between the reference measure and the optional
measure. Inspired by Maenhout[19]
Branger[20]
the problem is modified to define the value function as:
V(t, x, l. h) = ð¸ð‘¡,ð‘¥,ð‘™,â„Ž
ð‘ƒÎ¦
0−
1
ð›¾
ð‘’−ð›¾ð‘‹(ð‘‡)
+ ∫ ðº(ð‘¢, ð‘‹ðœ€(ð‘¢), ðœ™(ð‘¢))ð‘‘ð‘¢
ð‘‡
ð‘¡
1
Φ∈Σ
ð‘–ð‘›ð‘“
ðœ€âˆˆð›±
ð‘ ð‘¢ð‘
ð¸ð‘¡,ð‘¥,ð‘™,â„Ž
ð‘ƒÎ¦
Calculated under the optional measure , the initial value of the stochastic process is ð‘‹ðœ€(ð‘¡)=x, S(t)=s,
H(t)=h,
G(u, Xε(u), ϕ(u)) =
Φ0
2
2Ψ0(t, Xε(t), ϕ(t))
+
Φ1
2
2Ψ1(t, Xε(t), ϕ(t))
+
Φ2
2
2Ψ2(t, Xε(t), ϕ(t))
+
(Φ3 ln Φ3 − Φ3 + 1)hp
(1 − h)
2Ψ3(t, Xε(t), ϕ(t))
Where Ψ0 ≥ 0,Ψ1 ≥ 0,Ψ2 ≥ 0,Ψ3 ≥ 0 is state-dependent,let Ψ0 = −
ð‘£0
ð›¾V(t,x,l,h)
, Ψ1 = −
ð‘£1
ð›¾V(t,x,l,h)
, Ψ2 =
−
ð‘£2
ð›¾V(t,x,l,h)
, Ψ3 = −
ð‘£3
ð›¾V(t,x,l,h)
ð‘£ð‘–,i=0,1,2,3 is the risk aversion factor, the lager Ψi. According to the dynamic planning principle, the HJB
equation is as follows:
ð’œðœ€,ðœ™
𑉠+ ðº(ð‘¢, ð‘‹ðœ€(ð‘¢), ðœ™(ð‘¢)) = 0
Φðœ–Σ
ð‘–ð‘›ð‘“
ðœ€ðœ–âˆ
ð‘ ð‘¢ð‘
#(3)
ð’œðœ€,ðœ™
is the infinitesimal operator under the measure ð‘ƒÎ¦
.
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 94
III. Robust optimal reinsurance-investment strategy solving
This section will solve the robust optimal problem constructed in the previous section. This paper
divides the value function into pre-default and post-default components according to the time of default of the
credit bond:
V(T, x, l, h) = {
V(T, x, l, 0),h = 0(before default)
V(T, x, l, 1),h = 1(after default)
By decomposing the value function into two sub-functions, denoted as the value function before the zero-
coupon bond default and the value function after the zero-coupon bond default, the two sub-HJB equations are
obtained and solved successively to obtain the reinsurance and risky asset investment strategies and value
function expressions after default, and the reinsurance, risky asset and credit bond investment strategies and
value function expressions before default.
1.5 Optimal reinsurance and investment decisions after default
When H (t)=1,τ ∧ T ≤ t ≤ T,the insurer has constituted a default at or before time t, the HJB equation
degenerates to:
ð‘‰ð‘¡ +
[ð‘Ÿð‘¥ + ðœ‹(ð›¼ð‘™ − Φ1√ð‘™) + ðœ†Î¼X(θ1 − η1) + λpμY(θ2 − η2) + ðœ†Î¼Xη1ð‘ž1(ð‘¡) + λpμYη2ð‘ž2(ð‘¡) +
√(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï
Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2Φ0]ð‘‰
ð‘¥ +
1
2
(Ï€2
l + λ(q1ςX)2
+ λp(q2ςY)2
+ 2λpμXμY)Vxx + Ï€lÏ‚ÏVxl +
(k(ω − l) − Φ1ðœðœŒâˆšð‘™ − Φ2ðœâˆš1 − ðœŒ2√ð‘™)Vl +
1
2
Ï‚2
lVll −
Φ0
2
2v0
𛾠−
Φ1
2
2v1
𛾠−
Φ2
2
2v2
𛾠= 0 (4)
Satisfied :V(T, x, l, 1) = −
1
γ
e−γX
The solution can be assumed to be of the form:
V(t, x, y, l, 1) = −
1
γ
exp*−γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
x + G(t, l)+, G(T, l) = 0#(5)
Taking each partial derivative of V:
{
ð‘‰ð‘¡ = [γrxð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ Gt]V, ð‘‰
ð‘¥ = −γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
V
ð‘‰
ð‘¥ð‘¥ = γ2
ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ð‘‰ï¼Œð‘‰ð‘¥ð‘™ = −γðºð‘™ð‘‰
ð‘‰ð‘™ = ðºð‘™ð‘‰, ð‘‰ð‘™ð‘™ = ðºð‘™ð‘™ð‘‰ + ðºð‘™
2
ð‘‰
The minimum value point of Φ∗
is obtained from the first order condition as:
{
Φ0
∗
= v0er(T−t)
√(q1γ1)2 + (q2γ2)2 + 2Ï
̂q1q2γ1γ2
Φ1
∗
= v1er(T−t)
π√l, Φ2
∗
= −ςÏ√lGlv2
1
γ
Bringing in the HJB equation yields:
γrxð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ Gt − ,λμX(θ1 − η1) + λpμY(θ2 − η2)-
γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ k(ω − l)ðºð‘™ +
(ðœðœŒâˆšð‘™ðºð‘™)
2
v2
2
+
1
2
ðœ2
ð‘™(ðºð‘™ð‘™ + ðºð‘™
2
)
+ *ð‘“2(ðœ‹, ð‘¡)+
Ï€
inf
+ {λγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ð‘“1(ð‘ž1, ð‘ž2, ð‘¡)}
ð‘ž1,ð‘ž2
inf
= 0#(6)
Where
ð‘“1(ð‘ž1, ð‘ž2, ð‘¡) = −,μXη1ð‘ž1(ð‘¡) + pμYη2ð‘ž2(ð‘¡)-
+
(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
2
,(ð‘ž1ðœð‘‹)2
+ p(ð‘ž2ðœð‘Œ)2
+ 2pÏ‚XÏ‚Yð‘ž1ð‘ž2-
ð‘“2(ðœ‹, ð‘¡) = ðœ‹ð‘™ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(Ï‚Ïðºð‘™(γ + v1) − ð›¼) +
1
2
(γ + v1)lπ2
ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡)
Theorem III.1 Let m=
μX(η1ðœŽð‘Œ
2−pη2μY
2)
ðœŽð‘¥
2ðœŽð‘Œ
2−ð‘μX
2μY
2 , n=
μY(η2ðœŽð‘‹
2−η1μX
2)
ðœŽð‘¥
2ðœŽð‘Œ
2−ð‘μX
2μY
2 ,then there exist ð‘¡1, ð‘¡2ð‘¡1
Ì‚, ð‘¡2
Ì‚ and the following values
can be obtained:
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 95
ð‘¡1 = 𑇠−
1
ð‘Ÿ
ln
ð‘š
γ + v0
, ð‘¡2 = 𑇠−
1
ð‘Ÿ
ln
ð‘›
γ + v0
ð‘¡1
̂ = 𑇠−
1
ð‘Ÿ
ln
μXη1
(γ + v0)p(ðœð‘‹
2 + μXμY)
ð‘¡2
̂ = 𑇠−
1
ð‘Ÿ
ln
μyη2
(γ + v0)(ðœð‘Œ
2 + μXμY)
When m ≤ γ(n ≤ γ),let ð‘¡2 = ð‘‡(ð‘¡1 = ð‘‡).When m > γ(n > γ),let ð‘¡2 = 0(ð‘¡1 = 0)(1)If 𑚠≤ n,then ð‘ž1
∗
≤ ð‘ž2
∗
,for
all tϵ,0, T-,The reinsurance strategy corresponding to the problem is(ð‘ž1
∗
, ð‘ž2
∗
) = {
(ð‘ž1
Ì‚ , ð‘ž2
Ì‚),0 ≤ 𑡠≤ ð‘¡2
(ð‘ž1
̃, 1
̃),ð‘¡2 ≤ 𑡠≤ ð‘¡1
Ì‚
(1,1),ð‘¡1 ≤ 𑡠≤ ð‘‡
(2)If
n > m,then for alltϵ,0, T-,The reinsurance strategy corresponding to the problem
is(ð‘ž1
∗
, ð‘ž2
∗
) = {
(ð‘ž1
Ì‚ , ð‘ž2
Ì‚),0 ≤ 𑡠≤ ð‘¡1
(1, ð‘ž2
̃), ð‘¡1 ≤ 𑡠≤ ð‘¡2
Ì‚
(1,1), ð‘¡2
Ì‚ ≤ 𑡠≤ ð‘‡
. Where
ð‘ž1
Ì‚ =
μX(η1ðœð‘Œ
2
− pη2μY
2)
(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
#(7)
ð‘ž2
Ì‚ =
μY(η2ðœð‘‹
2
− η1μX
2)
(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
#(8)
ð‘ž1
̃ =
μXη1 − pμXμY(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ðœð‘‹
2(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)p
#(9)
ð‘ž2
̃ =
μyη2 − μXμY(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ðœð‘Œ
2(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
#(10)
Proof:By finding the first-order partial derivatives, second-order partial derivatives and second-order mixed
partial derivatives forð‘“1, the following system of equations and the Hessian array are obtained:
{
ðœ•ð‘“1
ðœ•ð‘ž1
= −μXη1 + (γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
,ðœð‘‹
2
ð‘ž1 + pÏ‚XÏ‚Yð‘ž2- = 0
ðœ•ð‘“1
ðœ•ð‘ž2
= −μYη2 + (γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
,ðœð‘Œ
2
ð‘ž2 + Ï‚XÏ‚Yð‘ž1- = 0
(11)
|
|
ðœ•2
ð‘“1
ðœ•ð‘ž1ðœ•ð‘ž1
ðœ•2
ð‘“1
ðœ•ð‘ž1ðœ•ð‘ž2
ðœ•2
ð‘“1
ðœ•ð‘ž2ðœ•ð‘ž1
ðœ•2
ð‘“1
ðœ•ð‘ž2ðœ•ð‘ž2
|
| = ð‘’4ð‘Ÿ(ð‘‡âˆ’ð‘¡)
(γ + v0)2
|
−ðœð‘¥
2
(γ + v0) −pςXςY
−pÏ‚XÏ‚Y −ð‘ðœð‘¦
2
(γ + v0)
|
From the Hessian array positive definite it is known that ð‘“1(ð‘ž1, ð‘ž2, ð‘¡) is a convex function and there exist
extreme value points; solving the system of equations (11) yields (7). (8).
Obviously,ð‘ž1
Ì‚ ã€ð‘ž2
Ì‚ are both increasing functions with respect to t, when 𑚠≤ n,0 ≤ 𑡠≤ ð‘¡1 or n > m,0 ≤
𑡠≤ ð‘¡2the solution as (7)(8),Also the values of ð‘¡1 and ð‘¡2 can be found. When 𑚠≤ n,ð‘¡2 ≤ 𑡠≤ ð‘¡1
̂ ,then
(q1
∗
, q2
∗
) = (ð‘ž1
̃, 1),q1 ∈ ,0,1-.When ð‘› > m,ð‘¡1 ≤ 𑡠≤ ð‘¡2
Ì‚ then (q1
∗
, q2
∗
) = (1, ð‘ž1
̃), q2 ∈ ,0,1-,Separate solve
df1(t,q1,1)
dq1
= 0,
df1(t,1,q2)
dq2
= 0 , then can get ð‘ž1
̃, ð‘ž2
̃ as (9), (10) End.
Theorem III.2 The post-default insurer's optimal risky asset investment strategy is to
π∗
=
α − Ï‚Ï(γ + v1)ðº1
(γ + v1)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
#(12)
The expression of the optimal value function is:
V(t, x, y, l, 1) = −
1
γ
exp*−γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(t)x + G1(t)l + G2(t)+#(13)
ð‘¤ð‘•ð‘’ð‘Ÿð‘’ Ï â‰  ±1, ðº1 =
ð‘™1ð‘™2 − ð‘™1ð‘™2ð‘’−
1
2
Ï‚2(ð‘™1−ð‘™2)(γ+v1)(1−Ï2)(ð‘‡âˆ’ð‘¡)
ð‘™2 − ð‘™1ð‘’−
1
2
Ï‚2(ð‘™1−ð‘™2)(γ+v1)(1−Ï2)(ð‘‡âˆ’ð‘¡)
, #(14)
Ï = 1, ðº1 =
α2
2(γ + v1)(ας + k)
(1 − ð‘’−(ας+k)(ð‘‡âˆ’ð‘¡)
), #(15)
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 96
Ï = −1, k ≠ ας, ðº1 =
α2
2(γ + v1)(𑘠− ας)
(1 − ð‘’(ας−k)(ð‘‡âˆ’ð‘¡)
), #(16)
Ï = −1, 𑘠= ας, ðº1 =
α2
2(γ + v1)
, #(17)
ð‘™1,2 =
−(Î±Ï‚Ï + k) ± √(Î±Ï‚Ï + k)2 + α2Ï‚2(1 − Ï2)
γς2(1 − Ï2)
G2 =
γ
r
,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,1 − ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
-
+ð‘˜ðœ” ∫ G1(s)ds
ð‘‡
ð‘¡
+ ∫ γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ð‘“1(ð‘ž1
∗
, ð‘ž2
∗
, ð‘ )ð‘‘ð‘ 
ð‘‡
ð‘¡
#(18)
Proof: Let
G(t, l) = G1(t)l + G2(t)#(19)
Bringing equation (19) into equation (6) can be obtained as the following two equations:
G1
’
−
α2
2(γ + v1)
− G1(Î±Ï‚Ï + k) +
1
2
(γ + v1)ς2
G1
2
(Ï2
− 1) = 0#(20)
G2‘ − ,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ð‘˜ðœ”G1 + λγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ð‘“1(ð‘ž1
∗
, ð‘ž2
∗
, ð‘¡) = 0#(21)
Solving equation (20) yields equations (14)-(17). From equation (21) we get (18), and the specific expression of
(18) is discussed in the following cases:
1)When 𑚠≤ n,0 ≤ 𑡠≤ ð‘¡2(n > m, 0 ≤ 𑡠≤ ð‘¡1)
G2 =
γ
ð‘Ÿ
,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1- + G1(t)
Ì‚
−λ(T − t)*μXη1
μX(η1ðœð‘Œ
2
− pη2μY
2)
(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
+ pμYη2
μY(η2ðœð‘‹
2
− pη1μX
2)
(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
−
1
2
,(
μXðœð‘‹(η1ðœð‘Œ
2
− pη2μY
2)
(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
)
2
+ p (
μYðœð‘Œ(η2ðœð‘‹
2
− pη1μX
2)
(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
)
2
+2pςXςY
μX(η1ðœð‘Œ
2
− pη2μY
2
)
(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
μY(η2ðœð‘‹
2
− pη1μX
2
)
(ðœð‘¥
2ðœð‘Œ
2 − ð‘μX
2μY
2)
-+
2)When 𑚠≤ ð‘›, ð‘¡2 ≤ 𑡠≤ ð‘¡1
Ì‚,
G2 =
γ
r
,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1-
+
ðœ†ð›¾
(𛾠+ v0)
(
μXη1
ðœð‘‹ð‘
)
2
(
1
2
− p)(T − t) + λ(−
μXη1pμXμY
ðœð‘‹
2p
−λpμYη2 +
μXη1μXμY
ðœð‘‹
+ Ï‚Y
μXη1
Ï‚X
)
γ
r
(ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1)
+,(
μXμY
ðœð‘‹
)
2
+ pðœð‘Œ
2
− 2ð‘Ï‚Y
μXμY
ðœð‘‹
-
λγ(𛾠+ v0)
2r
(ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1) + ð‘˜ðœ”G1(t)
Ì‚
3)When ð‘š > ð‘›, ð‘¡1 ≤ 𑡠≤ ð‘¡2
Ì‚,optimal reinsurance strategy (ð‘ž1
∗
, ð‘ž2
∗
) =(1,ð‘ž2
̃),
G2 =
γ
r
,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1-
+
λγ
(γ + ðœˆ0)
(
μyη2
ðœð‘Œ
)
2
(
1
2p
− 1) (T − t) + ð‘˜ðœ”G1(t)
Ì‚
+λμyη2 (μXη1 − ð‘μYη2
μXμY
ðœð‘Œ
2
− ςX
μyη2
ðœð‘Œ
+
μyη2μXμY
2ðœð‘Œ
2
)
γ(ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1)
r
+(ðœð‘‹
2
− 2pςX
μXμY
ðœð‘Œ
+ p(
μXμY
ðœð‘Œ
)2
)
λð›¾(𛾠+ v0)
4r
(ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1)
4) When ð‘š > ð‘›, ð‘¡2
Ì‚ ≤ 𑡠≤ T(𑚠≤ ð‘›, ð‘¡1
Ì‚ ≤ 𑡠≤ ð‘‡), optimal reinsurance strategy (ð‘ž1
∗
, ð‘ž2
∗
) =(1,1),
G2 =
γ
r
,λμXθ1 + λpμYθ2-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1-
+ð‘˜ðœ”G1(t)
Ì‚ +
λγ(γ + v0)
4
,(ðœð‘‹)2
+ p(ðœð‘Œ)2
+ 2pÏ‚XÏ‚Y-(ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡)
− 1)
Where G1(t)
̂ = kω ∫ G1(s)ds
T
t
=
ð‘™2ð‘˜ðœ”(𑇠− ð‘¡) − 2ð‘˜ðœ”(ðœ2
(1 − ðœŒ2
)−1
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 97
∗ ð‘™ð‘›|
ð‘™1 − ð‘™2
ð‘™1 − ð‘™2ð‘’0.5ðœŽ2(ð‘™1−ð‘™2)(1−ðœŒ2)(γ+v1)(ð‘‡âˆ’ð‘¡)
|)ï¼ŒÏ â‰  ±1
α2
ð‘˜ðœ”
2(𑘠+ ας)(γ + v1)
(T − t) +
1
2
(
α
(k + ας)(γ + v1)
)2
ð‘˜ðœ”(1 − ð‘’(ð‘˜+ας)(ð‘‡âˆ’ð‘¡)
)ï¼ŒÏ = 1
α2
ð‘˜ðœ”
2(𑘠− ας)(γ + v1)
(T − t) +
1
2
(
α
(k − ας)(γ + v1)
)2
ð‘˜ðœ”(1 − ð‘’(ð‘˜âˆ’ας)(ð‘‡âˆ’ð‘¡)
)ï¼ŒÏ = −1, k ≠ ας
ð‘˜ðœ”
,(T−t)α-2
4(γ+v1)
ï¼ŒÏ = −1,k = ας. End.
1.6 Optimal reinsurance and investment decisions before default
This section considers the optimal pre-default reinsurance-investment strategy and the value function expression
based on the previous section, when H(t)=0, 0 ≤ t ≤ τ ∧ T.Let the solution of the default prior value function
have the following form:
V(T, x, l, 0) = −
1
ð›¾
ð‘’ð‘¥ð‘{−ð›¾ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(ð‘¡)ð‘¥ + ð¾(ð‘¡, ð‘™)}#(22)
Satisfying the boundary conditions V(T, x, l, 0)=V(x), K(T, l)=0, the HJB equation is transformed into:
ð‘‰ð‘¡ + ,ðœ‹(ð›¼ð‘™ − Φ1√ð‘™) + βδ(1 − Δ) + λμX(θ1 + η1ð‘ž1(ð‘¡) − 1))
+λpμY .θ2 + η2(ð‘ž2(ð‘¡) − 1)√(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï
Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2Φ01 ð‘‰
ð‘¥
+
1
2
((ðœ‹)2
ð‘™ + λ(ð‘ž1ðœð‘‹)2
+ λp(ð‘ž2ðœð‘Œ)2
+ 2λpðœð‘‹ðœð‘Œ)ð‘‰
ð‘¥ð‘¥
+ðœ‹ð‘™ðœÏð‘‰ð‘¥ð‘™ + (k(ω − l) − Φ1ðœðœŒâˆšð‘™ − Φ2ðœâˆš1 − ðœŒ2√ð‘™))Vl +
1
2
Ï‚2
lVll
+ð‘‰(ð‘’ð›¾Î²(t)ζð»1(ð‘¡)+ð¾(ð‘¡,ð‘™)−G(ð‘¡,ð‘™)
− 1)ð‘•ð‘
−
Φ0
2
2v0
𛾠−
Φ1
2
2v1
𛾠−
Φ2
2
2v2
𛾠−
(Φ3 ln Φ3 − Φ3 + 1)hp
(1 − h)
2v2
𛾠= 0
Similarly find the partial derivative of V:
{
ð‘‰ð‘¡ = [γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ Kt’]V, ð‘‰
ð‘¥ = −γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
V
ð‘‰
ð‘¥ð‘¥ = γ2
ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ð‘‰ï¼Œð‘‰ð‘¥ð‘™ = −γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ð¾ð‘™ð‘‰
ð‘‰ð‘™ = ð¾ð‘™ð‘‰, ð‘‰ð‘™ð‘™ = ð¾ð‘™ð‘™ð‘‰ + ð¾ð‘™
2
ð‘‰
Bringing the above expression into the HJB equation and fixing the reinsurance-investment strategy, the
minimum point of Φ is obtained according to the first-order condition as:
{
Φ0
∗
= v0ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
√(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï
Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2
Φ1
∗
= v1ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ðœ‹âˆšð‘™, Φ2
∗
= −ðœðœŒâˆšð‘™Kð‘™v2
1
ð›¾
Φ3
∗
= ð‘’ð‘¥ð‘*
v3
ð›¾
.ð‘’−ð›¾Î²(t)ζð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)+ðº1(ð‘¡,ð‘™)−G(ð‘¡,ð‘™)
− 1/+
#(23)
After bringing (23) into the HJB equation, by inverting the investment strategy we can obtain:
π∗
=
α − Ï‚Ï(γ + v1)Kl
(γ + v1)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
, β∗
=
ln
1
∆Φ3
+ K(t, l) − G(t, l)
ζγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
and obviously the expressions for the reinsurance strategy before and after the bond default are the same, so that
ð‘”1(ð‘¡, q1, q2) = ð‘“1(ð‘¡, q1, q2) = −,μXη1q1 + pμYη2q2-
+
1
2
,(q1Ï‚X)2
+ p(q2Ï‚Y)2
+ pςXςYμXμYγ2
-(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
Bringing ε∗
= (π∗
, β∗
, ð‘ž1
∗
, ð‘ž2
∗
) into the equation, after finishing, we get:
,−γð‘Ÿð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ Kt’- − ,λμX(θ1 − η1)
+λpμY(θ2 − η2)-γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ k(ω − l)Kl +
1
2
Ï‚2
l(Kll + Kl
2
)
−λγer(T−t)
ð‘”1(q1
∗
, q2
∗
, t) − g2(π∗
, t) − g3(β∗
, t) = 0#(24)
Where
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 98
ð‘”2(π∗
, t) = π∗
ð‘™ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(Ï‚Ïð¾ð‘™(γ + v1) − ð›¼) +
1
2
(γ + v1)lπ∗2
ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) (25)
ð‘”3(β∗
, t) = −
(Φ3 − 1)γhp
v3
− δβγer(T−t)
#(26)
The derivative of equation (26) with respect to β :
β∗
=
ln
1
∆Φ3
+ K(t, l) − G(t, l)
ζγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
#(27)
Bringing it into Φ3
∗
get :
hp
v3
Φ3(ð‘¡) ln Φ3(ð‘¡) + hp
Φ3(ð‘¡) −
ð›¿
ðœ
= 0. The equation has dimension one positive roots
Φ3.
Let K(t, l)=K1(t)l + K2(t),satisfy the boundary conditions K1(T)=0,K2(T) = 0,bring it to HJB equation(24),
eliminating the effect of l on the equation yields two equations:
K1
’
− kð¾1 +
1
2
Ï‚2
ð¾1
2
−
ð¾1 − ðº1
ζ
δ − (Ï‚Ïð¾1 + α(δ − r))α(δ − r)
+
1
2
(Ï‚Ïð¾1 + α(δ − r))
2
− (Ï‚Ïð¾1 + α(δ − r))Ï‚Ïð¾1 = 0#(28)
K2
’
− ,λμX(θ1 − η1) + λpμY(θ2 − η2)-γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
+ λpςXςYγ2
(ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
)2
+kωð¾1 −
ln
1
∆Φ3
+ ð¾2 − ðº2
ζ
δ + (1 −
1
∆Φ3
) hp
− f(t, ð‘ž1
∗
, ð‘ž2
∗) = 0#(29)
When Ï â‰  ±1,equation (28) is the first-order RICCATI equation that,from the existence uniqueness of the
solution ð¾1 = ðº1.Then we solve equation(29):let I(t)=ð¾2 − ðº2, Satisfying the boundary condition I(T) = 0, then
using (29) and (21) we get:I’ = K2
’
− G2
’
=
δ
ζ
I +
δ
ζ
ln
1
∆Φ3
+
γ(Φ3−1)
v3
hp
,
I = (ln
1
∆Φ3
+ ∆ − 1)ð‘’
−
δ
ζ
(T−t)
− ln
1
∆Φ3
− ∆ + 1.Thus :
ð¾2 = (ln
1
∆Φ3
+
γ∆(Φ3 − 1)
v3
) ð‘’
−
δ
ζ
(T−t)
− ln
1
∆Φ3
+
γ∆(Φ3 − 1)
v3
+ ðº2(30)
Theorem III.3 The optimal pre-default investment and bond investment strategies are:
π∗
=
α − Ï‚Ï(γ + v1)Kl
(γ + v1)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
, ð›½âˆ—
=
ð‘£3ln
1
ΔΦ3
+ Δð›¾(Φ3 − 1)(ð‘’
−
ð›¿
ðœ
(T−t)
− 1)
ð‘£3ðœð›¾ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
The expression of the value function before default is:
ð‘‰(ð‘¡, ð‘¥, ð‘™, 0) = −
1
ð›¾
exp{−ð›¾ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)
ð‘¥ + K1(ð‘¡)ð‘™+K2(ð‘¡)+
Where K1(t) = G1(t),as the formula (14)-(17),K2(t) as the formula (30).
IV. Parameter Sensitivity analysis
In this chapter, we give several numerical examples to test the effect of model parameters on the
optimal strategy. First, to make the parameters more realistic, the model parameters for credit bonds are set as
follows, based on the estimates from Berndt (2008)[22]
and Collin-Dufrensn & Solnik (2001)[23],
which are
estimated from market data:1/Δ = 2.53, hQ
= 0.013, ðœ = 0.52.The claim amounts for the first and second
categories of insurance respectively meet the parameters of λ𑋠= 1.5, λ𑌠= 1exponential distribution . If no
special statement is made, other model parameters are assumed as follows:: t = 3, T = 10, 𑟠= 0.06, 𛾠=
4,η1 = 2, η2 = 3, p = 0.5, ðœˆ0 = ðœˆ1 = ðœˆ3 = 1, Ï = 1, Ï‚ = 0.16, 𑘠= 2, α = 1.5.
1.7 Influence of parameters on optimal reinsurance strategy
Figure.1-2 represents the variation of the optimal reinsurance strategy with the parameters. where Figure.1
shows the variation of reinsurance strategy with probability p. When p increases, the insurer will reduce the
amount of reinsurance retention for class I reinsurance and increase the amount of reinsurance retention for class
II reinsurance. figure.2 represents the effect of risk aversion coefficient 𛾠on reinsurance strategy, when the risk
aversion coefficient is larger, the insurer will reduce the reinsurance strategy and purchase more reinsurance to
diversify Claims risk.
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 99
Figure. 1 Figure. 2
1.8 Influence of parameters on optimal investment strategy
Where Figure.3 represents the effect of the risk-free rate r on the optimal investment strategyπ∗
, when the risk-
free rate increases, the insurer will invest less in risky assets and more assets in risk-free assets. Figure.4
represents the effect of the volatile reversion rate k on the optimal investment strategyπ∗
. When the reversion
rate increases, the insurer will increase its investment in risky assets.
Figure. 3 Figure. 4
Figure.5 shows the impact of risk premium
1
Δ
on credit bonds, when the risk premium increases, investment in
credit bonds is increased. Figure.6 indicates that when the default loss rate ðœ increases, insurers will invest less
in credit bond.
Figure. 5 Figure. 6
1.9 Influence of ambiguity aversion coefficient on strategy
Figure.7 to Figure.9 represent the effect of optimal reinsurance-investment strategy subject to ambiguity
aversion sparsity. It can be seen that as the ambiguity aversion coefficient increases, the insurer's uncertainty
about the model increases and therefore reduces its optimal reinsurance-investment strategy.
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6
p
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
q1
q2
2 2.5 3 3.5 4 4.5 5 5.5 6
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
q1
q2
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
r
0.05
0.1
0.15
0.2
0.25
0.3
1 1.5 2 2.5 3 3.5 4 4.5 5
k
0.222
0.2225
0.223
0.2235
0.224
0.2245
0.225
0.2255
0.226
1 2 3 4 5 6 7 8
1/
0
0.5
1
1.5
2
2.5
3
3.5
4
1
, =1.5
2
, =2.53
3
, =5
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0
0.5
1
1.5
2
2.5
3
3.5
1
,1/ =1.5
2
,1/ =2.53
3
,1/ =5
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 100
Figure. 7 Figure. 8
Figure. 9
V. Conclusion
This paper assumes that the insurer owns two types of insurance business with sparse dependence risk,
and the claim process is described by a diffusion approximation model, and secondly, the insurer expands its
investment types by investing in the financial market with a stock, a risk-free asset and a credit bond, with the
stock price described by a Heston model and the credit bond price described by an approximate model. The
credit bond price is described by the approximate model, and considering that the insurer is ambiguous averse,
the robust optimal reinsurance-investment problem is established, and the explicit expressions of the robust
optimal reinsurance-investment and optimal value function are obtained by using stochastic control theory,
dynamic programming principle, and HJB equation, and sensitivity analysis is performed on the model
parameters. Based on this paper, further discussions can be made: 1) other situations of the claim process can be
considered: such as jump diffusion or common shock. 2) time lag effects can be considered. 3) game problems
can be considered.
References
[1]. Browne S . Optimal investment policies for a firm with a random risk process: Exponential utility and
minimizing the probability of ruin[J]. Mathematics of Operations Research, 1995, 20(4):937-958.
[2]. Zhang Y , Zhao P , Teng X , et al. Optimal reinsurance and investment strategies for an insurer and a
reinsurer under Hestons SV model: HARA utility and Legendre transform[J]. Journal of Industrial and
Management Optimization, 2017, 13(5).
[3]. Zhu S , Shi J . Optimal Reinsurance and Investment Strategies Under Mean-Variance Criteria: Partial
and Full Information[J]. Journal of Systems Science and Complexity: English Edition, 2022, 35(4):22.
[4]. LI, Danping, RONG, et al. Optimal Investment Problem for an Insurer and a Reinsurer[J]. Journal of
Systems Science and Complexity: English Edition.,2015(6):18.
[5]. A D L , B X R A , A H Z . Time-consistent reinsurance–investment strategy for an insurer and a
reinsurer with mean–variance criterion under the CEV model[J]. Journal of Computational and Applied
Mathematics, 2015, 283:142-162.
[6]. Chun-Xiang A , Gu A L , Shao Y . Optimal Reinsurance and Investment Strategy with Delay in
Heston's SV Model[J]. Journal of the Chinese Society of Operations Research (English), 2021, 9(2):27.
[7]. Xiaoqin Gong, Shixia Ma, Qing Huang,, Robust optimal investment strategies for insurance and
reinsurance companies under stochastic interest rates and stochastic volatility (in English) [J]. Journal
of Nankai University: Natural Science Edition, 2019, 52(6):11.
[8]. Grandell J . Aspects of Risk Theory[M]. World Publishing Co. 1991.
[9]. Zhao H , Rong X , Zhao Y . Optimal excess-of-loss reinsurance and investment problem for an insurer
with jump-diffusion risk process under the Heston model[J]. INSURANCE -AMSTERDAM-, 2013.
[10]. Ceci C , Colaneri K , Cretarola A . Optimal reinsurance and investment under common shock
dependence between financial and actuarial markets[J]. Insurance: Mathematics and Economics, 2022,
105.
[11]. Zhang P . Optimal excess-of-loss reinsurance and investment problem with thinning dependent risks
under Heston model[J]. Journal of Computational and Applied Mathematics, 2021, 382(1).
[12]. Li S , Qiu Z . Optimal Time-Consistent Investment and Reinsurance Strategies with Default Risk and
Delay under Heston's SV Model[J]. Mathematical Problems in Engineering, 2021, 2021(1):1-36.
[13]. Zhu G . Time-consistent non-zero-sum stochastic differential reinsurance and investment game under
default and volatility risks[J]. Journal of Computational and Applied Mathematics, 2020, 374.
[14]. Zhenlong Chen, Weijie Yuan, Dengfeng Xia. Optimal Reinsurance-Investment Strategy with Default
Risk Based on Heston's SV Model [J]. Business Economics and Management, 2021, 000(005):56-70.
0 1 2 3 4 5 6 7 8 9 10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
q1
q2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
1
0.1
0.15
0.2
0.25
1 1.5 2 2.5 3 3.5 4
3
0.3442
0.34425
0.3443
0.34435
0.3444
0.34445
0.3445
0.34455
0.3446
1
Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 101
[15]. Bo Y , Li Z , Viens F G , et al. Robust optimal control for an insurer with reinsurance and investment
under Heston's stochastic volatility model[J]. Insurance: Mathematics and Economics, 2013,
53(3):601-614.
[16]. Hui Meng, Li Wei, Ming Zhou. Robust reinsurance strategies for insurers under ambiguous aversion
[J]. Science of China:Mathematics, 2021, 51(11):28.
[17]. Zhang Y , Zhao P . Robust Optimal Excess-of-Loss Reinsurance and Investment Problem with Delay
and Dependent Risks[J]. Discrete Dynamics in Nature and Society, 2019, 2019(2):1-21.
[18]. Bielecki T R , Jang I . Portfolio optimization with a defaultable security[J]. Kluwer Academic
Publishers-Plenum Publishers, 2007(2).
[19]. Maenhout P J . Robust Portfolio Rules and Asset Pricing[J]. Review of Financial Studies, 2004(4):4.
[20]. Branger N , Larsen L S . Robust portfolio choice with uncertainty about jump and diffusion risk[J].
Journal of Banking & Finance, 2013, 37(12):1397-1411.
[21]. Shreve S E . Stochastic Calculus for Finance ll[M]. World Book Publishing, 2007.
[22]. Berndt A , Douglas R , Duffie D , et al. Measuring Default Risk Premia from Default Swap Rates and
EDFs[C]// Bank for International Settlements. Bank for International Settlements, 2005:1–18.
[23]. Collin-Dufresne P , Solnik B . On the Term Structure of Default Premia in the Swap and LIBOR
Markets[J]. Journal of Finance, 2001, 56(3):p.1095-1116.

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Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default risks

  • 1. International Journal of Business Marketing and Management (IJBMM) Volume 8 Issue 2 Mar-Apr 2023, P.P. 91-101 ISSN: 2456-4559 www.ijbmm.com International Journal of Business Marketing and Management (IJBMM) Page 91 Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default risks Yingqi Liang1 , Peibiao Zhao1 1 School of Mathematics and Statistics,Nanjing University of Science and Technology, Nanjing Jiangsu 210094,China 843186823@ Abstract: In this paper, we consider an AAI with two types of insurance business with p-thinning dependent claims risk, diversify claims risk by purchasing proportional reinsurance, and invest in a stock with Heston model price process, a risk-free bond, and a credit bond in the financial market with the objective of maximizing the expectation of the terminal wealth index effect, and construct the wealth process of AAI as well as the the model of robust optimal reinsurance-investment problem is obtained, using dynamic programming, the HJB equation to obtain the pre-default and post-default reinsurance-investment strategies and the display expression of the value function, respectively, and the sensitivity of the model parameters is analyzed through numerical experiments to obtain a realistic economic interpretation. The model as well as the results in this paper are a generalization and extension of the results of existing studies. Key words: p-Thinning dependent risk, defaultable bonds, dynamic programming, HJB equation, robust optimization. I. Introduction The sound operation and solid claiming ability of insurance companies are important to maintain social stability and promote social development, and the purchase of reinsurance can well control the risk of insurance companies. The current research on reinsurance in the actuarial field of insurance mainly focuses on the insurer's objective function, investment type, claim process, and price process of assets. [1]-[3]studied the most available reinsurance investment problems under different utility function. [4]-[7]investigate the optimal reinsurance investment problem under different risky asset price process. Most of the current literature considers only single-risk claims, while in reality the risks are usually correlated with each other. The current literature on claim dependency risk is divided into two main types of dependency, one is co-impact and the other is p-thinning dependency. P-thinning dependency means that when one type of claim occurs, there is a certain probability p that another type of claim will occur, for example, a car accident or fire will not only cause property damage, but also loss of life if the situation is serious. The problem under diffusion approximation model, jump diffusion risk model is studied in[8][9],[10] studied the type of dependent risk for common shocks, and [11] considered the risk process under p-thinning dependence. Most of the current studies consider only two assets for considering investments in credit bonds. [12]-[14] take into account defaulted bonds among the types of investments for insurers. Since models with diffusion and jump terms usually introduce uncertainty in the model for insurers, insurers usually want to seek a more robust model. [15]-[17] study the AAI most reinsurance-investment problem. Based on this, this paper studies the optimal proportional reinsurance-investment problem of AAI under the Heston model by considering both sparse dependence and claims risk based on [11][14][17]. The paper is organized as follows: a robust optimal reinsurance-investment problem model under p-thinning dependence and default risk is developed in Section 2. The value function is divided into pre-default and post-default in Section 3, and the optimal reinsurance-investment strategies are solved for pre-default and post-default using dynamic programming, optimal control theory, and the HJB equation, respectively. Parameter sensitivities are analyzed, and economic explanations are given in Section 4. Section 5 concludes the paper. II. Model Formulation Suppose *Ω, F, *ð¹ð‘¡+t∈,0,T -, P+ is a complete probability space, the positive number T denotes the final value moment, [0, T ] is a fixed time interval, ð¹ð‘¡ denotes the information in the market up to time t, and 𔽠∶= *ð¹ð‘¡+t∈,0,T -denotes the standard Brownian motion ð‘Š0(ð‘¡), ð‘Š1(ð‘¡), ð‘Š2(ð‘¡), ð‘Š3(ð‘¡). Poisson process N(t), and the right-continuous P-complete information flow generated by the sequence of random variables *ð‘‹ð‘–, 𑖠≥ 1+, *ð‘Œð‘–, 𑖠≥ 1+. ℠∶= (â„‹ð‘¡)t⩾0 is the information flow generated by the violation process H(t), let ð”¾: = (ð’¢ð‘¡)t⩾0, be the information flow generated by ð”½, â„ the expanded information flow, i.e., ð”¾: = ℱ𑡠∨ â„‹ð‘¡. By definition, each 𔽠-harness is also the 𔾠-harness. The probability measure P is a realistic probability measure and Q is a risk- neutral measure. In addition, it is assumed that all transactions in the financial market are continuous, and no
  • 2. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 92 taxes do not incur transaction costs and all property is infinitely divisible. 1.1 Surplus Process Assuming that the insurer operates two different lines of business and that there is a sparse dependency between these two lines of business, the surplus process is as follows: R(t) = ð‘¥0 + ð‘𑡠− (∑ ð‘‹ð‘– ð‘(ð‘¡) ð‘–=1 + ∑ ð‘Œð‘– ð‘ð‘(ð‘¡) ð‘–=1 ) . #(1) where{ð‘‹ð‘–,𑖠≥ 1} is independently and identically distributed in ð¹ð‘‹(∙),ð¸(ð‘‹) = ðœ‡ð‘‹ > 0,ð¸(ð‘‹2 ) = ðœð‘‹ 2 , as the claim amount of the first class of business,{ð‘Œð‘–,𑖠≥ 1} is independently and identically distributed inð¹ð‘Œ(∙ ),ð¸(ð‘Œ) = ðœ‡ð‘Œ > 0,ð¸(ð‘Œ2 ) = ðœð‘Œ 2 , as the claim amount of the second class of business. the claim amount of the second type of business. N(t)denotes the conforming Poisson process with parameter c denotes the premium of the insurance company by the expected value premium there are c = (1 + θ1)λðœ‡ð‘‹ + (1 + θ2)λpðœ‡ð‘Œ.θ1 > 0,θ2 > 0. 1.2 Proportional Reinsurance Assuming that the insurer diversifies the claim risk by purchasing proportional reinsurance, and let ð‘ž1(ð‘¡),ð‘ž2(ð‘¡) be the insurer's retention ratio, the claim after the insurer purchases reinsurance is: ð‘ž1(ð‘¡)ð‘‹ð‘– , ð‘ž2(ð‘¡)ð‘Œð‘– then the reinsurance fee is δ(ð‘ž1(ð‘¡), ð‘ž2(ð‘¡)) = (1 + η1)(1 − ð‘ž1(ð‘¡))λðœ‡ð‘‹ + (1 + η2)(1 − ð‘ž2(ð‘¡))λpðœ‡ð‘Œ.According to Grandell(1991)[8] ,the claims process can be diffusely approximated as: d ∑ Xi N(t) i=1 = λE(Xi)dt − γ1dWX(t), γ1 = √λE(XI 2 ) d ∑ Yi Np(t) i=1 = λE(Yi)dt − γ2dWY(t), γ2 = √λE(YI 2 ) The correlation coefficient of ð‘Šð‘‹(ð‘¡)ð‘Šð‘Œ(ð‘¡ )is Ï Ì‚ = λp ð›¾1ð›¾2 E(ð‘‹ð‘–)E(ð‘Œð‘–).Then the wealth process of the insurer after joining the reinsurance is: dXq1,q2 = ,λμX(θ1 − η1 + η1ð‘ž1(ð‘¡)) + λpμY(θ2 − η2 +η2ð‘ž2(ð‘¡))ð‘‘ð‘¡ + √(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2dW0 1.3 Financial Market Suppose the financial market consists of three assets: risk-free assets, stocks, and corporate bonds, and the price processes of the three assets are as follows: The price process of risk-free bonds is given by:ð‘‘R(t) = rR(t)dt.The stock price process S(t) obeys the Heston stochastic volatility model: { ð‘‘ð‘†(ð‘¡) = ð‘†(ð‘¡),ð‘Ÿ + ð›¼ð¿(ð‘¡)ð‘‘ð‘¡ + √ð¿(ð‘¡)ð‘‘ð‘Š1(ð‘¡)-, ð‘†(0) = ð‘ 0 ð‘‘ð¿(ð‘¡) = ð‘˜(𜔠− ð¿(ð‘¡))ð‘‘ð‘¡ + ðœâˆšð¿(ð‘¡)ð‘‘ð‘Š2(ð‘¡), ð¿(0) = ð‘™0 R is the risk-free rate,α, ð‘˜, Ï‚, are positive constant.ð¸,ð‘Š1ð‘Š2- = Ït, 2ð‘˜ðœ” ≥ Ï‚2 Following Bielecki (2007)[18] , the credit bond price process p(t, T1), under a realistic measure P, using an approximate model to portray default risk is as follows: dp(t, T1) = p(t−, T1),(r + (1 − H(t))δ(1 − Δ)dt −(1 − H(t−))ζdMp (t)- Where Mp (t) = H(t) − hQ ∫ Δ(1 − H(u))du t 0 is aâ„Š − harness, δ = ð‘•ð‘„ ζ is the credit spread. 1.4 Robust optimization problem Assuming the insurer adopts a reinsurance investment strategyε(t) = (ð‘ž1(ð‘¡), ð‘ž2(ð‘¡), Ï€(t), β(ð‘¡)),ð‘ž1(ð‘¡), ð‘ž2(ð‘¡)are the reinsurance strategies adopted by the insurer at moment t in the first and second asset classes, respectively.Ï€(t) for the insurance company's investment in equities at time t.,β(ð‘¡)for the insurance company′s investment in credit bonds at time t. Let 𔸠denotes the set of all feasible strategies, then the dynamic process of wealth of the insurance company at this moment ð‘‹ðœ€ (t) is: dð‘‹ðœ€(ð‘¡) = ðœ‹(ð‘¡) ð‘‘ð‘†(ð‘¡) ð‘†(ð‘¡) + β(ð‘¡) ð‘‘ð‘(ð‘¡) ð‘(ð‘¡) + (ð‘‹ðœ€(ð‘¡) − ðœ‹(ð‘¡) − β(ð‘¡)) ð‘‘ðµ(ð‘¡) ðµ(ð‘¡)
  • 3. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 93 +ð‘‘ð‘‹ð‘š(ð‘¡),Xε(0) = x0 Assume that the insurer maximizes the terminal T moment expected utility in the financial market, the portfolio index utility, which takes the form of: V(X(T)) = − 1 𛾠ð‘’−ð›¾ð‘‹(ð‘‡) Where 𛾠> 0 is the ambiguity aversion coefficient of the insurer. The insurer's goal is to find the optimal reinsurance-investment strategyðœ€âˆ— (ð‘¡) = (ð‘ž1 ∗ (ð‘¡), ð‘ž2 ∗ (ð‘¡), ðœ‹âˆ— (ð‘¡), β∗ (ð‘¡))to maximizing the expectation of end-use wealth utility for insurers. The objective function of the insurer is: Vε (t, x, l, h) = E(u(Xε (T))|Xε (t) = x, L(t) = l) The value function of the optimization problem is: V(t, x, l, h) = Vε (t, x, l, h) ε∈Π sup , V(T,x,l,h)=v(x), Assume that the ambiguity information is described by the probability P and the reference model is measured by the probability ð’«Î¦ which is equivalent to P:ð’«: = *ð’«Î¦ |ð’«Î¦ ~ð‘ƒ+.Next, the optional measure set is constructed, defining the procedure :Φ(ð‘¡) = (Φ0(ð‘¡), Φ1(ð‘¡), Φ2(ð‘¡), Φ3(ð‘¡))s.t.: 1. Φ(ð‘¡) is a â„Š(ð‘¡)- measurable for any t[0,T] 2. Φi(t) = Φi(t, ω), i = 0,1,2,3 andΦi(t) ≥ 0 for all (t, ω) ∈ ,0, T- × Ω. 3.∫ ||Φ(t)||2 ð‘‘ð‘¡ < ∞; 𑇠0 Let Σ be all processes shaped as Φ,for all Φ ∈ Σ define a G-adaptation process under a real measure *ΛΦ (ð‘¡)|𑡠∈ ,0, T-+.From Ito differentiation we have: ð‘‘ΛΦ (ð‘¡) = ΛΦ (ð‘¡âˆ’)(−Φ0(ð‘¡)dW0 − Φ1(ð‘¡)ð‘‘ð‘Š1 − Φ2(ð‘¡)ð‘‘ð‘Š2 − (1 − Φ3(ð‘¡))ð‘‘Mp ) Where ΛΦ (0) = 1,P-a.s. ΛΦ (ð‘¡) is a (P,G)- martingale,E[ΛΦ (ð‘‡)] =1, for each Φ ∈ Σ,A new optional measure is absolutely continuous to P, defined as ð‘‘ð‘ƒÎ¦ ð‘‘𑃠|ð’¢ð‘‡ = ΛΦ (ð‘‡). So far, we have constructed a class of real-world probability measures ð‘ƒÎ¦ ,where Φ ∈ Σ,From Gisanova's theorem[21] ,it follows that: ð‘‘Wi ð‘ƒÎ¦ (ð‘¡) = dWi(ð‘¡) + Φð‘–(ð‘¡)ð‘‘ð‘¡, ð‘– = 0,1,2 Therefore the wealth process in the ð‘ƒÎ¦ is: dð‘‹ðœ€ (ð‘¡) = ,xr + ðœ‹(ð›¼ð‘™ − Φ1√ð‘™) + β(1 − H(t))δ(1 − Δ) +λμX(θ1 − η1) + λpμY((θ2 − η2) + η1ð‘ž1(ð‘¡)) + η2ð‘ž2(ð‘¡)) +√(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2Φ0-dt + ðœ‹âˆšð‘™ð‘‘W1 ð‘ƒÎ¦ +β(1 − H(t−))ζdMp + √(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2ð‘‘W0 ð‘ƒÎ¦ (2) We assume that the insurer determines a robust portfolio strategy such that the worst-case scenario is the best option. The insurer penalizes any deviation from the sub-reference model with a penalty that increases with this deviation, using relative entropy to measure the deviation between the reference measure and the optional measure. Inspired by Maenhout[19] Branger[20] the problem is modified to define the value function as: V(t, x, l. h) = ð¸ð‘¡,ð‘¥,ð‘™,â„Ž ð‘ƒÎ¦ 0− 1 𛾠ð‘’−ð›¾ð‘‹(ð‘‡) + ∫ ðº(ð‘¢, ð‘‹ðœ€(ð‘¢), ðœ™(ð‘¢))ð‘‘𑢠𑇠𑡠1 Φ∈Σ ð‘–ð‘›ð‘“ ðœ€âˆˆð›± ð‘ ð‘¢ð‘ ð¸ð‘¡,ð‘¥,ð‘™,â„Ž ð‘ƒÎ¦ Calculated under the optional measure , the initial value of the stochastic process is ð‘‹ðœ€(ð‘¡)=x, S(t)=s, H(t)=h, G(u, Xε(u), Ï•(u)) = Φ0 2 2Ψ0(t, Xε(t), Ï•(t)) + Φ1 2 2Ψ1(t, Xε(t), Ï•(t)) + Φ2 2 2Ψ2(t, Xε(t), Ï•(t)) + (Φ3 ln Φ3 − Φ3 + 1)hp (1 − h) 2Ψ3(t, Xε(t), Ï•(t)) Where Ψ0 ≥ 0,Ψ1 ≥ 0,Ψ2 ≥ 0,Ψ3 ≥ 0 is state-dependent,let Ψ0 = − ð‘£0 ð›¾V(t,x,l,h) , Ψ1 = − ð‘£1 ð›¾V(t,x,l,h) , Ψ2 = − ð‘£2 ð›¾V(t,x,l,h) , Ψ3 = − ð‘£3 ð›¾V(t,x,l,h) ð‘£ð‘–,i=0,1,2,3 is the risk aversion factor, the lager Ψi. According to the dynamic planning principle, the HJB equation is as follows: ð’œðœ€,𜙠𑉠+ ðº(ð‘¢, ð‘‹ðœ€(ð‘¢), ðœ™(ð‘¢)) = 0 Φðœ–Σ ð‘–ð‘›ð‘“ ðœ€ðœ–∠ð‘ ð‘¢ð‘ #(3) ð’œðœ€,𜙠is the infinitesimal operator under the measure ð‘ƒÎ¦ .
  • 4. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 94 III. Robust optimal reinsurance-investment strategy solving This section will solve the robust optimal problem constructed in the previous section. This paper divides the value function into pre-default and post-default components according to the time of default of the credit bond: V(T, x, l, h) = { V(T, x, l, 0),h = 0(before default) V(T, x, l, 1),h = 1(after default) By decomposing the value function into two sub-functions, denoted as the value function before the zero- coupon bond default and the value function after the zero-coupon bond default, the two sub-HJB equations are obtained and solved successively to obtain the reinsurance and risky asset investment strategies and value function expressions after default, and the reinsurance, risky asset and credit bond investment strategies and value function expressions before default. 1.5 Optimal reinsurance and investment decisions after default When H (t)=1,τ ∧ T ≤ t ≤ T,the insurer has constituted a default at or before time t, the HJB equation degenerates to: ð‘‰ð‘¡ + [ð‘Ÿð‘¥ + ðœ‹(ð›¼ð‘™ − Φ1√ð‘™) + ðœ†Î¼X(θ1 − η1) + λpμY(θ2 − η2) + ðœ†Î¼Xη1ð‘ž1(ð‘¡) + λpμYη2ð‘ž2(ð‘¡) + √(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2Φ0]𑉠𑥠+ 1 2 (Ï€2 l + λ(q1Ï‚X)2 + λp(q2Ï‚Y)2 + 2λpμXμY)Vxx + Ï€lÏ‚ÏVxl + (k(ω − l) − Φ1ðœðœŒâˆšð‘™ − Φ2ðœâˆš1 − ðœŒ2√ð‘™)Vl + 1 2 Ï‚2 lVll − Φ0 2 2v0 𛾠− Φ1 2 2v1 𛾠− Φ2 2 2v2 𛾠= 0 (4) Satisfied :V(T, x, l, 1) = − 1 γ e−γX The solution can be assumed to be of the form: V(t, x, y, l, 1) = − 1 γ exp*−γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) x + G(t, l)+, G(T, l) = 0#(5) Taking each partial derivative of V: { ð‘‰ð‘¡ = [γrxð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) + Gt]V, 𑉠𑥠= −γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) V 𑉠ð‘¥ð‘¥ = γ2 ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) ð‘‰ï¼Œð‘‰ð‘¥ð‘™ = −γðºð‘™ð‘‰ ð‘‰ð‘™ = ðºð‘™ð‘‰, ð‘‰ð‘™ð‘™ = ðºð‘™ð‘™ð‘‰ + ðºð‘™ 2 𑉠The minimum value point of Φ∗ is obtained from the first order condition as: { Φ0 ∗ = v0er(T−t) √(q1γ1)2 + (q2γ2)2 + 2Ï Ì‚q1q2γ1γ2 Φ1 ∗ = v1er(T−t) π√l, Φ2 ∗ = −ςÏ√lGlv2 1 γ Bringing in the HJB equation yields: γrxð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) + Gt − ,λμX(θ1 − η1) + λpμY(θ2 − η2)- γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) + k(ω − l)ðºð‘™ + (ðœðœŒâˆšð‘™ðºð‘™) 2 v2 2 + 1 2 ðœ2 ð‘™(ðºð‘™ð‘™ + ðºð‘™ 2 ) + *ð‘“2(ðœ‹, ð‘¡)+ Ï€ inf + {λγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ð‘“1(ð‘ž1, ð‘ž2, ð‘¡)} ð‘ž1,ð‘ž2 inf = 0#(6) Where ð‘“1(ð‘ž1, ð‘ž2, ð‘¡) = −,μXη1ð‘ž1(ð‘¡) + pμYη2ð‘ž2(ð‘¡)- + (γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) 2 ,(ð‘ž1ðœð‘‹)2 + p(ð‘ž2ðœð‘Œ)2 + 2pÏ‚XÏ‚Yð‘ž1ð‘ž2- ð‘“2(ðœ‹, ð‘¡) = ðœ‹ð‘™ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(Ï‚Ïðºð‘™(γ + v1) − ð›¼) + 1 2 (γ + v1)lÏ€2 ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) Theorem III.1 Let m= μX(η1ðœŽð‘Œ 2−pη2μY 2) ðœŽð‘¥ 2ðœŽð‘Œ 2−ð‘μX 2μY 2 , n= μY(η2ðœŽð‘‹ 2−η1μX 2) ðœŽð‘¥ 2ðœŽð‘Œ 2−ð‘μX 2μY 2 ,then there exist ð‘¡1, ð‘¡2ð‘¡1 Ì‚, ð‘¡2 Ì‚ and the following values can be obtained:
  • 5. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 95 ð‘¡1 = 𑇠− 1 ð‘Ÿ ln 𑚠γ + v0 , ð‘¡2 = 𑇠− 1 ð‘Ÿ ln 𑛠γ + v0 ð‘¡1 Ì‚ = 𑇠− 1 ð‘Ÿ ln μXη1 (γ + v0)p(ðœð‘‹ 2 + μXμY) ð‘¡2 Ì‚ = 𑇠− 1 ð‘Ÿ ln μyη2 (γ + v0)(ðœð‘Œ 2 + μXμY) When m ≤ γ(n ≤ γ),let ð‘¡2 = ð‘‡(ð‘¡1 = ð‘‡).When m > γ(n > γ),let ð‘¡2 = 0(ð‘¡1 = 0)(1)If 𑚠≤ n,then ð‘ž1 ∗ ≤ ð‘ž2 ∗ ,for all tϵ,0, T-,The reinsurance strategy corresponding to the problem is(ð‘ž1 ∗ , ð‘ž2 ∗ ) = { (ð‘ž1 Ì‚ , ð‘ž2 Ì‚),0 ≤ 𑡠≤ ð‘¡2 (ð‘ž1 ̃, 1 ̃),ð‘¡2 ≤ 𑡠≤ ð‘¡1 Ì‚ (1,1),ð‘¡1 ≤ 𑡠≤ 𑇠(2)If n > m,then for alltϵ,0, T-,The reinsurance strategy corresponding to the problem is(ð‘ž1 ∗ , ð‘ž2 ∗ ) = { (ð‘ž1 Ì‚ , ð‘ž2 Ì‚),0 ≤ 𑡠≤ ð‘¡1 (1, ð‘ž2 ̃), ð‘¡1 ≤ 𑡠≤ ð‘¡2 Ì‚ (1,1), ð‘¡2 Ì‚ ≤ 𑡠≤ 𑇠. Where ð‘ž1 Ì‚ = μX(η1ðœð‘Œ 2 − pη2μY 2) (γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) #(7) ð‘ž2 Ì‚ = μY(η2ðœð‘‹ 2 − η1μX 2) (γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) #(8) ð‘ž1 ̃ = μXη1 − pμXμY(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ðœð‘‹ 2(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)p #(9) ð‘ž2 ̃ = μyη2 − μXμY(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ðœð‘Œ 2(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) #(10) Proof:By finding the first-order partial derivatives, second-order partial derivatives and second-order mixed partial derivatives forð‘“1, the following system of equations and the Hessian array are obtained: { ðœ•ð‘“1 ðœ•ð‘ž1 = −μXη1 + (γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ,ðœð‘‹ 2 ð‘ž1 + pÏ‚XÏ‚Yð‘ž2- = 0 ðœ•ð‘“1 ðœ•ð‘ž2 = −μYη2 + (γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ,ðœð‘Œ 2 ð‘ž2 + Ï‚XÏ‚Yð‘ž1- = 0 (11) | | ðœ•2 ð‘“1 ðœ•ð‘ž1ðœ•ð‘ž1 ðœ•2 ð‘“1 ðœ•ð‘ž1ðœ•ð‘ž2 ðœ•2 ð‘“1 ðœ•ð‘ž2ðœ•ð‘ž1 ðœ•2 ð‘“1 ðœ•ð‘ž2ðœ•ð‘ž2 | | = ð‘’4ð‘Ÿ(ð‘‡âˆ’ð‘¡) (γ + v0)2 | −ðœð‘¥ 2 (γ + v0) −pÏ‚XÏ‚Y −pÏ‚XÏ‚Y −ð‘ðœð‘¦ 2 (γ + v0) | From the Hessian array positive definite it is known that ð‘“1(ð‘ž1, ð‘ž2, ð‘¡) is a convex function and there exist extreme value points; solving the system of equations (11) yields (7). (8). Obviously,ð‘ž1 Ì‚ ã€ð‘ž2 Ì‚ are both increasing functions with respect to t, when 𑚠≤ n,0 ≤ 𑡠≤ ð‘¡1 or n > m,0 ≤ 𑡠≤ ð‘¡2the solution as (7)(8),Also the values of ð‘¡1 and ð‘¡2 can be found. When 𑚠≤ n,ð‘¡2 ≤ 𑡠≤ ð‘¡1 Ì‚ ,then (q1 ∗ , q2 ∗ ) = (ð‘ž1 ̃, 1),q1 ∈ ,0,1-.When ð‘› > m,ð‘¡1 ≤ 𑡠≤ ð‘¡2 Ì‚ then (q1 ∗ , q2 ∗ ) = (1, ð‘ž1 ̃), q2 ∈ ,0,1-,Separate solve df1(t,q1,1) dq1 = 0, df1(t,1,q2) dq2 = 0 , then can get ð‘ž1 ̃, ð‘ž2 ̃ as (9), (10) End. Theorem III.2 The post-default insurer's optimal risky asset investment strategy is to π∗ = α − Ï‚Ï(γ + v1)ðº1 (γ + v1)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) #(12) The expression of the optimal value function is: V(t, x, y, l, 1) = − 1 γ exp*−γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(t)x + G1(t)l + G2(t)+#(13) ð‘¤ð‘•ð‘’ð‘Ÿð‘’ Ï â‰  ±1, ðº1 = ð‘™1ð‘™2 − ð‘™1ð‘™2ð‘’− 1 2 Ï‚2(ð‘™1−ð‘™2)(γ+v1)(1−Ï2)(ð‘‡âˆ’ð‘¡) ð‘™2 − ð‘™1ð‘’− 1 2 Ï‚2(ð‘™1−ð‘™2)(γ+v1)(1−Ï2)(ð‘‡âˆ’ð‘¡) , #(14) Ï = 1, ðº1 = α2 2(γ + v1)(ας + k) (1 − ð‘’−(ας+k)(ð‘‡âˆ’ð‘¡) ), #(15)
  • 6. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 96 Ï = −1, k ≠ ας, ðº1 = α2 2(γ + v1)(𑘠− ας) (1 − ð‘’(ας−k)(ð‘‡âˆ’ð‘¡) ), #(16) Ï = −1, 𑘠= ας, ðº1 = α2 2(γ + v1) , #(17) ð‘™1,2 = −(Î±Ï‚Ï + k) ± √(Î±Ï‚Ï + k)2 + α2Ï‚2(1 − Ï2) γς2(1 − Ï2) G2 = γ r ,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,1 − ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) - +ð‘˜ðœ” ∫ G1(s)ds 𑇠𑡠+ ∫ γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ð‘“1(ð‘ž1 ∗ , ð‘ž2 ∗ , ð‘ )ð‘‘𑠠𑇠𑡠#(18) Proof: Let G(t, l) = G1(t)l + G2(t)#(19) Bringing equation (19) into equation (6) can be obtained as the following two equations: G1 ’ − α2 2(γ + v1) − G1(Î±Ï‚Ï + k) + 1 2 (γ + v1)Ï‚2 G1 2 (Ï2 − 1) = 0#(20) G2‘ − ,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) +ð‘˜ðœ”G1 + λγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ð‘“1(ð‘ž1 ∗ , ð‘ž2 ∗ , ð‘¡) = 0#(21) Solving equation (20) yields equations (14)-(17). From equation (21) we get (18), and the specific expression of (18) is discussed in the following cases: 1)When 𑚠≤ n,0 ≤ 𑡠≤ ð‘¡2(n > m, 0 ≤ 𑡠≤ ð‘¡1) G2 = γ ð‘Ÿ ,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1- + G1(t) Ì‚ −λ(T − t)*μXη1 μX(η1ðœð‘Œ 2 − pη2μY 2) (ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) + pμYη2 μY(η2ðœð‘‹ 2 − pη1μX 2) (ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) − 1 2 ,( μXðœð‘‹(η1ðœð‘Œ 2 − pη2μY 2) (ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) ) 2 + p ( μYðœð‘Œ(η2ðœð‘‹ 2 − pη1μX 2) (ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) ) 2 +2pÏ‚XÏ‚Y μX(η1ðœð‘Œ 2 − pη2μY 2 ) (ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) μY(η2ðœð‘‹ 2 − pη1μX 2 ) (ðœð‘¥ 2ðœð‘Œ 2 − ð‘μX 2μY 2) -+ 2)When 𑚠≤ ð‘›, ð‘¡2 ≤ 𑡠≤ ð‘¡1 Ì‚, G2 = γ r ,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1- + ðœ†ð›¾ (𛾠+ v0) ( μXη1 ðœð‘‹ð‘ ) 2 ( 1 2 − p)(T − t) + λ(− μXη1pμXμY ðœð‘‹ 2p −λpμYη2 + μXη1μXμY ðœð‘‹ + Ï‚Y μXη1 Ï‚X ) γ r (ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1) +,( μXμY ðœð‘‹ ) 2 + pðœð‘Œ 2 − 2ð‘Ï‚Y μXμY ðœð‘‹ - λγ(𛾠+ v0) 2r (ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1) + ð‘˜ðœ”G1(t) Ì‚ 3)When ð‘š > ð‘›, ð‘¡1 ≤ 𑡠≤ ð‘¡2 Ì‚,optimal reinsurance strategy (ð‘ž1 ∗ , ð‘ž2 ∗ ) =(1,ð‘ž2 ̃), G2 = γ r ,λ(μX(θ1 − η1) + λp(μY(θ2 − η2)-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1- + λγ (γ + ðœˆ0) ( μyη2 ðœð‘Œ ) 2 ( 1 2p − 1) (T − t) + ð‘˜ðœ”G1(t) Ì‚ +λμyη2 (μXη1 − ð‘μYη2 μXμY ðœð‘Œ 2 − Ï‚X μyη2 ðœð‘Œ + μyη2μXμY 2ðœð‘Œ 2 ) γ(ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1) r +(ðœð‘‹ 2 − 2pÏ‚X μXμY ðœð‘Œ + p( μXμY ðœð‘Œ )2 ) λð›¾(𛾠+ v0) 4r (ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1) 4) When ð‘š > ð‘›, ð‘¡2 Ì‚ ≤ 𑡠≤ T(𑚠≤ ð‘›, ð‘¡1 Ì‚ ≤ 𑡠≤ ð‘‡), optimal reinsurance strategy (ð‘ž1 ∗ , ð‘ž2 ∗ ) =(1,1), G2 = γ r ,λμXθ1 + λpμYθ2-,ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1- +ð‘˜ðœ”G1(t) Ì‚ + λγ(γ + v0) 4 ,(ðœð‘‹)2 + p(ðœð‘Œ)2 + 2pÏ‚XÏ‚Y-(ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) − 1) Where G1(t) Ì‚ = kω ∫ G1(s)ds T t = ð‘™2ð‘˜ðœ”(𑇠− ð‘¡) − 2ð‘˜ðœ”(ðœ2 (1 − ðœŒ2 )−1
  • 7. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 97 ∗ ð‘™ð‘›| ð‘™1 − ð‘™2 ð‘™1 − ð‘™2ð‘’0.5ðœŽ2(ð‘™1−ð‘™2)(1−ðœŒ2)(γ+v1)(ð‘‡âˆ’ð‘¡) |)ï¼ŒÏ â‰  ±1 α2 ð‘˜ðœ” 2(𑘠+ ας)(γ + v1) (T − t) + 1 2 ( α (k + ας)(γ + v1) )2 ð‘˜ðœ”(1 − ð‘’(ð‘˜+ας)(ð‘‡âˆ’ð‘¡) )ï¼ŒÏ = 1 α2 ð‘˜ðœ” 2(𑘠− ας)(γ + v1) (T − t) + 1 2 ( α (k − ας)(γ + v1) )2 ð‘˜ðœ”(1 − ð‘’(ð‘˜âˆ’ας)(ð‘‡âˆ’ð‘¡) )ï¼ŒÏ = −1, k ≠ ας ð‘˜ðœ” ,(T−t)α-2 4(γ+v1) ï¼ŒÏ = −1,k = ας. End. 1.6 Optimal reinsurance and investment decisions before default This section considers the optimal pre-default reinsurance-investment strategy and the value function expression based on the previous section, when H(t)=0, 0 ≤ t ≤ Ï„ ∧ T.Let the solution of the default prior value function have the following form: V(T, x, l, 0) = − 1 𛾠ð‘’ð‘¥ð‘{−ð›¾ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(ð‘¡)ð‘¥ + ð¾(ð‘¡, ð‘™)}#(22) Satisfying the boundary conditions V(T, x, l, 0)=V(x), K(T, l)=0, the HJB equation is transformed into: ð‘‰ð‘¡ + ,ðœ‹(ð›¼ð‘™ − Φ1√ð‘™) + βδ(1 − Δ) + λμX(θ1 + η1ð‘ž1(ð‘¡) − 1)) +λpμY .θ2 + η2(ð‘ž2(ð‘¡) − 1)√(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2Φ01 𑉠𑥠+ 1 2 ((ðœ‹)2 ð‘™ + λ(ð‘ž1ðœð‘‹)2 + λp(ð‘ž2ðœð‘Œ)2 + 2λpðœð‘‹ðœð‘Œ)𑉠ð‘¥ð‘¥ +ðœ‹ð‘™ðœÏð‘‰ð‘¥ð‘™ + (k(ω − l) − Φ1ðœðœŒâˆšð‘™ − Φ2ðœâˆš1 − ðœŒ2√ð‘™))Vl + 1 2 Ï‚2 lVll +ð‘‰(ð‘’ð›¾Î²(t)ζð»1(ð‘¡)+ð¾(ð‘¡,ð‘™)−G(ð‘¡,ð‘™) − 1)ð‘•ð‘ − Φ0 2 2v0 𛾠− Φ1 2 2v1 𛾠− Φ2 2 2v2 𛾠− (Φ3 ln Φ3 − Φ3 + 1)hp (1 − h) 2v2 𛾠= 0 Similarly find the partial derivative of V: { ð‘‰ð‘¡ = [γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) + Kt’]V, 𑉠𑥠= −γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) V 𑉠ð‘¥ð‘¥ = γ2 ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) ð‘‰ï¼Œð‘‰ð‘¥ð‘™ = −γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ð¾ð‘™ð‘‰ ð‘‰ð‘™ = ð¾ð‘™ð‘‰, ð‘‰ð‘™ð‘™ = ð¾ð‘™ð‘™ð‘‰ + ð¾ð‘™ 2 𑉠Bringing the above expression into the HJB equation and fixing the reinsurance-investment strategy, the minimum point of Φ is obtained according to the first-order condition as: { Φ0 ∗ = v0ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) √(ð‘ž1ð›¾1)2 + (ð‘ž2ð›¾2)2 + 2Ï Ì‚ð‘ž1ð‘ž2ð›¾1ð›¾2 Φ1 ∗ = v1ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ðœ‹âˆšð‘™, Φ2 ∗ = −ðœðœŒâˆšð‘™Kð‘™v2 1 𛾠Φ3 ∗ = ð‘’ð‘¥ð‘* v3 𛾠.ð‘’−ð›¾Î²(t)ζð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)+ðº1(ð‘¡,ð‘™)−G(ð‘¡,ð‘™) − 1/+ #(23) After bringing (23) into the HJB equation, by inverting the investment strategy we can obtain: π∗ = α − Ï‚Ï(γ + v1)Kl (γ + v1)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) , β∗ = ln 1 ∆Φ3 + K(t, l) − G(t, l) ζγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) and obviously the expressions for the reinsurance strategy before and after the bond default are the same, so that ð‘”1(ð‘¡, q1, q2) = ð‘“1(ð‘¡, q1, q2) = −,μXη1q1 + pμYη2q2- + 1 2 ,(q1Ï‚X)2 + p(q2Ï‚Y)2 + pÏ‚XÏ‚YμXμYγ2 -(γ + v0)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) Bringing ε∗ = (π∗ , β∗ , ð‘ž1 ∗ , ð‘ž2 ∗ ) into the equation, after finishing, we get: ,−γð‘Ÿð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) + Kt’- − ,λμX(θ1 − η1) +λpμY(θ2 − η2)-γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) + k(ω − l)Kl + 1 2 Ï‚2 l(Kll + Kl 2 ) −λγer(T−t) ð‘”1(q1 ∗ , q2 ∗ , t) − g2(π∗ , t) − g3(β∗ , t) = 0#(24) Where
  • 8. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 98 ð‘”2(π∗ , t) = π∗ ð‘™ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡)(Ï‚Ïð¾ð‘™(γ + v1) − ð›¼) + 1 2 (γ + v1)lπ∗2 ð‘’2ð‘Ÿ(ð‘‡âˆ’ð‘¡) (25) ð‘”3(β∗ , t) = − (Φ3 − 1)γhp v3 − δβγer(T−t) #(26) The derivative of equation (26) with respect to β : β∗ = ln 1 ∆Φ3 + K(t, l) − G(t, l) ζγð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) #(27) Bringing it into Φ3 ∗ get : hp v3 Φ3(ð‘¡) ln Φ3(ð‘¡) + hp Φ3(ð‘¡) − 𛿠ðœ = 0. The equation has dimension one positive roots Φ3. Let K(t, l)=K1(t)l + K2(t),satisfy the boundary conditions K1(T)=0,K2(T) = 0,bring it to HJB equation(24), eliminating the effect of l on the equation yields two equations: K1 ’ − kð¾1 + 1 2 Ï‚2 ð¾1 2 − ð¾1 − ðº1 ζ δ − (Ï‚Ïð¾1 + α(δ − r))α(δ − r) + 1 2 (Ï‚Ïð¾1 + α(δ − r)) 2 − (Ï‚Ïð¾1 + α(δ − r))Ï‚Ïð¾1 = 0#(28) K2 ’ − ,λμX(θ1 − η1) + λpμY(θ2 − η2)-γð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) + λpÏ‚XÏ‚Yγ2 (ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) )2 +kωð¾1 − ln 1 ∆Φ3 + ð¾2 − ðº2 ζ δ + (1 − 1 ∆Φ3 ) hp − f(t, ð‘ž1 ∗ , ð‘ž2 ∗) = 0#(29) When Ï â‰  ±1,equation (28) is the first-order RICCATI equation that,from the existence uniqueness of the solution ð¾1 = ðº1.Then we solve equation(29):let I(t)=ð¾2 − ðº2, Satisfying the boundary condition I(T) = 0, then using (29) and (21) we get:I’ = K2 ’ − G2 ’ = δ ζ I + δ ζ ln 1 ∆Φ3 + γ(Φ3−1) v3 hp , I = (ln 1 ∆Φ3 + ∆ − 1)𑒠− δ ζ (T−t) − ln 1 ∆Φ3 − ∆ + 1.Thus : ð¾2 = (ln 1 ∆Φ3 + γ∆(Φ3 − 1) v3 ) 𑒠− δ ζ (T−t) − ln 1 ∆Φ3 + γ∆(Φ3 − 1) v3 + ðº2(30) Theorem III.3 The optimal pre-default investment and bond investment strategies are: π∗ = α − Ï‚Ï(γ + v1)Kl (γ + v1)ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) , ð›½âˆ— = ð‘£3ln 1 ΔΦ3 + Δð›¾(Φ3 − 1)(𑒠− 𛿠ðœ (T−t) − 1) ð‘£3ðœð›¾ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) The expression of the value function before default is: ð‘‰(ð‘¡, ð‘¥, ð‘™, 0) = − 1 𛾠exp{−ð›¾ð‘’ð‘Ÿ(ð‘‡âˆ’ð‘¡) ð‘¥ + K1(ð‘¡)ð‘™+K2(ð‘¡)+ Where K1(t) = G1(t),as the formula (14)-(17),K2(t) as the formula (30). IV. Parameter Sensitivity analysis In this chapter, we give several numerical examples to test the effect of model parameters on the optimal strategy. First, to make the parameters more realistic, the model parameters for credit bonds are set as follows, based on the estimates from Berndt (2008)[22] and Collin-Dufrensn & Solnik (2001)[23], which are estimated from market data:1/Δ = 2.53, hQ = 0.013, ðœ = 0.52.The claim amounts for the first and second categories of insurance respectively meet the parameters of λ𑋠= 1.5, λ𑌠= 1exponential distribution . If no special statement is made, other model parameters are assumed as follows:: t = 3, T = 10, ð‘Ÿ = 0.06, 𛾠= 4,η1 = 2, η2 = 3, p = 0.5, ðœˆ0 = ðœˆ1 = ðœˆ3 = 1, Ï = 1, Ï‚ = 0.16, 𑘠= 2, α = 1.5. 1.7 Influence of parameters on optimal reinsurance strategy Figure.1-2 represents the variation of the optimal reinsurance strategy with the parameters. where Figure.1 shows the variation of reinsurance strategy with probability p. When p increases, the insurer will reduce the amount of reinsurance retention for class I reinsurance and increase the amount of reinsurance retention for class II reinsurance. figure.2 represents the effect of risk aversion coefficient 𛾠on reinsurance strategy, when the risk aversion coefficient is larger, the insurer will reduce the reinsurance strategy and purchase more reinsurance to diversify Claims risk.
  • 9. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 99 Figure. 1 Figure. 2 1.8 Influence of parameters on optimal investment strategy Where Figure.3 represents the effect of the risk-free rate r on the optimal investment strategyπ∗ , when the risk- free rate increases, the insurer will invest less in risky assets and more assets in risk-free assets. Figure.4 represents the effect of the volatile reversion rate k on the optimal investment strategyπ∗ . When the reversion rate increases, the insurer will increase its investment in risky assets. Figure. 3 Figure. 4 Figure.5 shows the impact of risk premium 1 Δ on credit bonds, when the risk premium increases, investment in credit bonds is increased. Figure.6 indicates that when the default loss rate ðœ increases, insurers will invest less in credit bond. Figure. 5 Figure. 6 1.9 Influence of ambiguity aversion coefficient on strategy Figure.7 to Figure.9 represent the effect of optimal reinsurance-investment strategy subject to ambiguity aversion sparsity. It can be seen that as the ambiguity aversion coefficient increases, the insurer's uncertainty about the model increases and therefore reduces its optimal reinsurance-investment strategy. 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 p 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 q1 q2 2 2.5 3 3.5 4 4.5 5 5.5 6 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 q1 q2 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 r 0.05 0.1 0.15 0.2 0.25 0.3 1 1.5 2 2.5 3 3.5 4 4.5 5 k 0.222 0.2225 0.223 0.2235 0.224 0.2245 0.225 0.2255 0.226 1 2 3 4 5 6 7 8 1/ 0 0.5 1 1.5 2 2.5 3 3.5 4 1 , =1.5 2 , =2.53 3 , =5 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.5 1 1.5 2 2.5 3 3.5 1 ,1/ =1.5 2 ,1/ =2.53 3 ,1/ =5
  • 10. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 100 Figure. 7 Figure. 8 Figure. 9 V. Conclusion This paper assumes that the insurer owns two types of insurance business with sparse dependence risk, and the claim process is described by a diffusion approximation model, and secondly, the insurer expands its investment types by investing in the financial market with a stock, a risk-free asset and a credit bond, with the stock price described by a Heston model and the credit bond price described by an approximate model. The credit bond price is described by the approximate model, and considering that the insurer is ambiguous averse, the robust optimal reinsurance-investment problem is established, and the explicit expressions of the robust optimal reinsurance-investment and optimal value function are obtained by using stochastic control theory, dynamic programming principle, and HJB equation, and sensitivity analysis is performed on the model parameters. Based on this paper, further discussions can be made: 1) other situations of the claim process can be considered: such as jump diffusion or common shock. 2) time lag effects can be considered. 3) game problems can be considered. References [1]. Browne S . Optimal investment policies for a firm with a random risk process: Exponential utility and minimizing the probability of ruin[J]. Mathematics of Operations Research, 1995, 20(4):937-958. [2]. Zhang Y , Zhao P , Teng X , et al. Optimal reinsurance and investment strategies for an insurer and a reinsurer under Hestons SV model: HARA utility and Legendre transform[J]. Journal of Industrial and Management Optimization, 2017, 13(5). [3]. Zhu S , Shi J . Optimal Reinsurance and Investment Strategies Under Mean-Variance Criteria: Partial and Full Information[J]. Journal of Systems Science and Complexity: English Edition, 2022, 35(4):22. [4]. LI, Danping, RONG, et al. Optimal Investment Problem for an Insurer and a Reinsurer[J]. Journal of Systems Science and Complexity: English Edition.,2015(6):18. [5]. A D L , B X R A , A H Z . Time-consistent reinsurance–investment strategy for an insurer and a reinsurer with mean–variance criterion under the CEV model[J]. Journal of Computational and Applied Mathematics, 2015, 283:142-162. [6]. Chun-Xiang A , Gu A L , Shao Y . Optimal Reinsurance and Investment Strategy with Delay in Heston's SV Model[J]. Journal of the Chinese Society of Operations Research (English), 2021, 9(2):27. [7]. Xiaoqin Gong, Shixia Ma, Qing Huang,, Robust optimal investment strategies for insurance and reinsurance companies under stochastic interest rates and stochastic volatility (in English) [J]. Journal of Nankai University: Natural Science Edition, 2019, 52(6):11. [8]. Grandell J . Aspects of Risk Theory[M]. World Publishing Co. 1991. [9]. Zhao H , Rong X , Zhao Y . Optimal excess-of-loss reinsurance and investment problem for an insurer with jump-diffusion risk process under the Heston model[J]. INSURANCE -AMSTERDAM-, 2013. [10]. Ceci C , Colaneri K , Cretarola A . Optimal reinsurance and investment under common shock dependence between financial and actuarial markets[J]. Insurance: Mathematics and Economics, 2022, 105. [11]. Zhang P . Optimal excess-of-loss reinsurance and investment problem with thinning dependent risks under Heston model[J]. Journal of Computational and Applied Mathematics, 2021, 382(1). [12]. Li S , Qiu Z . Optimal Time-Consistent Investment and Reinsurance Strategies with Default Risk and Delay under Heston's SV Model[J]. Mathematical Problems in Engineering, 2021, 2021(1):1-36. [13]. Zhu G . Time-consistent non-zero-sum stochastic differential reinsurance and investment game under default and volatility risks[J]. Journal of Computational and Applied Mathematics, 2020, 374. [14]. Zhenlong Chen, Weijie Yuan, Dengfeng Xia. Optimal Reinsurance-Investment Strategy with Default Risk Based on Heston's SV Model [J]. Business Economics and Management, 2021, 000(005):56-70. 0 1 2 3 4 5 6 7 8 9 10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 q1 q2 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 1 0.1 0.15 0.2 0.25 1 1.5 2 2.5 3 3.5 4 3 0.3442 0.34425 0.3443 0.34435 0.3444 0.34445 0.3445 0.34455 0.3446 1
  • 11. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris International Journal of Business Marketing and Management (IJBMM) Page 101 [15]. Bo Y , Li Z , Viens F G , et al. Robust optimal control for an insurer with reinsurance and investment under Heston's stochastic volatility model[J]. Insurance: Mathematics and Economics, 2013, 53(3):601-614. [16]. Hui Meng, Li Wei, Ming Zhou. Robust reinsurance strategies for insurers under ambiguous aversion [J]. Science of China:Mathematics, 2021, 51(11):28. [17]. Zhang Y , Zhao P . Robust Optimal Excess-of-Loss Reinsurance and Investment Problem with Delay and Dependent Risks[J]. Discrete Dynamics in Nature and Society, 2019, 2019(2):1-21. [18]. Bielecki T R , Jang I . Portfolio optimization with a defaultable security[J]. Kluwer Academic Publishers-Plenum Publishers, 2007(2). [19]. Maenhout P J . Robust Portfolio Rules and Asset Pricing[J]. Review of Financial Studies, 2004(4):4. [20]. Branger N , Larsen L S . Robust portfolio choice with uncertainty about jump and diffusion risk[J]. Journal of Banking & Finance, 2013, 37(12):1397-1411. [21]. Shreve S E . Stochastic Calculus for Finance ll[M]. World Book Publishing, 2007. [22]. Berndt A , Douglas R , Duffie D , et al. Measuring Default Risk Premia from Default Swap Rates and EDFs[C]// Bank for International Settlements. Bank for International Settlements, 2005:1–18. [23]. Collin-Dufresne P , Solnik B . On the Term Structure of Default Premia in the Swap and LIBOR Markets[J]. Journal of Finance, 2001, 56(3):p.1095-1116.