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.
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Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default risks
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) = π₯0 + ππ‘ β (β ππ
π(π‘)
π=1
+ β ππ
ππ(π‘)
π=1
) . #(1)
where{πποΌπ β₯ 1} is independently and identically distributed in πΉπ(β),πΈ(π) = ππ > 0οΌπΈ(π2
) = ππ
2
, as the
claim amount of the first class of businessοΌ{πποΌπ β₯ 1} is independently and identically distributed inπΉπ(β
),πΈ(π) = ππ > 0οΌπΈ(π2
) = ππ
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 + ΞΈ1)Ξ»ππ + (1 + ΞΈ2)Ξ»pππ.ΞΈ1 > 0,ΞΈ2 >
0.
1.2 Proportional Reinsurance
Assuming that the insurer diversifies the claim risk by purchasing proportional reinsurance, and let π1(π‘),π2(π‘)
be the insurer's retention ratio, the claim after the insurer purchases reinsurance is:
π1(π‘)ππ , π2(π‘)ππ then the reinsurance fee is Ξ΄(π1(π‘), π2(π‘)) = (1 + Ξ·1)(1 β π1(π‘))Ξ»ππ + (1 + Ξ·2)(1 β
π2(π‘))Ξ»pππ.According to Grandell(1991)[8]
,the claims process can be diffusely approximated as:
d β Xi
N(t)
i=1
= Ξ»E(Xi)dt β Ξ³1dWX(t), Ξ³1 = βΞ»E(XI
2
)
d β Yi
Np(t)
i=1
= Ξ»E(Yi)dt β Ξ³2dWY(t), Ξ³2 = βΞ»E(YI
2
)
The correlation coefficient of ππ(π‘)ππ(π‘ )is Ο
Μ =
Ξ»p
πΎ1πΎ2
E(ππ)E(ππ).Then the wealth process of the insurer after
joining the reinsurance is:
dXq1,q2 = ,λμX(ΞΈ1 β Ξ·1 + Ξ·1π1(π‘)) + Ξ»pΞΌY(ΞΈ2 β Ξ·2
+Ξ·2π2(π‘))ππ‘ + β(π1πΎ1)2 + (π2πΎ2)2 + 2Ο
Μπ1π2πΎ1πΎ2dW0
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 byοΌπR(t) =
rR(t)dt.The stock price process S(t) obeys the Heston stochastic volatility model:
{
ππ(π‘) = π(π‘),π + πΌπΏ(π‘)ππ‘ + βπΏ(π‘)ππ1(π‘)-, π(0) = π 0
ππΏ(π‘) = π(π β πΏ(π‘))ππ‘ + πβπΏ(π‘)ππ2(π‘), πΏ(0) = π0
R is the risk-free rate,Ξ±, π, Ο, are positive constant.πΈ,π1π2- = Οt, 2ππ β₯ Ο2
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(tβ, T1),(r + (1 β H(t))Ξ΄(1 β Ξ)dt
β(1 β H(tβ))ΞΆdMp
(t)-
Where Mp
(t) = H(t) β hQ
β« Ξ(1 β H(u))du
t
0
is aβ β harnessοΌ Ξ΄ = ππ
ΞΆ is the credit spread.
1.4 Robust optimization problem
Assuming the insurer adopts a reinsurance investment strategyΞ΅(t) = (π1(π‘), π2(π‘), Ο(t), Ξ²(π‘))οΌπ1(π‘), π2(π‘)are
the reinsurance strategies adopted by the insurer at moment t in the first and second asset classes,
respectively.Ο(t) for the insurance company's investment in equities at time t.οΌΞ²(π‘)for the insurance companyβ²s
investment in credit bonds at time t. Let πΈ denotes the set of all feasible strategies, then the dynamic process of
wealth of the insurance company at this moment ππ
(t) is:
dππ(π‘) = π(π‘)
ππ(π‘)
π(π‘)
+ Ξ²(π‘)
ππ(π‘)
π(π‘)
+ (ππ(π‘) β π(π‘) β Ξ²(π‘))
ππ΅(π‘)
π΅(π‘)
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)οΌh = 0(before default)
V(T, x, l, 1)οΌh = 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)=1οΌΟ β§ T β€ t β€ T,the insurer has constituted a default at or before time t, the HJB equation
degenerates toοΌ
ππ‘ +
[ππ₯ + π(πΌπ β Ξ¦1βπ) + πΞΌX(ΞΈ1 β Ξ·1) + Ξ»pΞΌY(ΞΈ2 β Ξ·2) + πΞΌXΞ·1π1(π‘) + Ξ»pΞΌYΞ·2π2(π‘) +
β(π1πΎ1)2 + (π2πΎ2)2 + 2Ο
Μπ1π2πΎ1πΎ2Ξ¦0]π
π₯ +
1
2
(Ο2
l + Ξ»(q1ΟX)2
+ Ξ»p(q2ΟY)2
+ 2Ξ»pΞΌXΞΌY)Vxx + ΟlΟΟVxl +
(k(Ο β l) β Ξ¦1ππβπ β Ξ¦2πβ1 β π2βπ)Vl +
1
2
Ο2
lVll β
Ξ¦0
2
2v0
πΎ β
Ξ¦1
2
2v1
πΎ β
Ξ¦2
2
2v2
πΎ = 0 (4)
Satisfied οΌV(T, x, l, 1) = β
1
Ξ³
eβΞ³X
The solution can be assumed to be of the form:
V(t, x, y, l, 1) = β
1
Ξ³
exp*βΞ³ππ(πβπ‘)
x + G(t, l)+, G(T, l) = 0#(5)
Taking each partial derivative of V:
{
ππ‘ = [Ξ³rxππ(πβπ‘)
+ Gt]V, π
π₯ = βΞ³ππ(πβπ‘)
V
π
π₯π₯ = Ξ³2
π2π(πβπ‘)
ποΌππ₯π = βΞ³πΊππ
ππ = πΊππ, πππ = πΊπππ + πΊπ
2
π
The minimum value point of Ξ¦β
is obtained from the first order condition as:
{
Ξ¦0
β
= v0er(Tβt)
β(q1Ξ³1)2 + (q2Ξ³2)2 + 2Ο
Μq1q2Ξ³1Ξ³2
Ξ¦1
β
= v1er(Tβt)
Οβl, Ξ¦2
β
= βΟΟβlGlv2
1
Ξ³
Bringing in the HJB equation yields:
Ξ³rxππ(πβπ‘)
+ Gt β ,λμX(ΞΈ1 β Ξ·1) + Ξ»pΞΌY(ΞΈ2 β Ξ·2)-
Ξ³ππ(πβπ‘)
+ k(Ο β l)πΊπ +
(ππβππΊπ)
2
v2
2
+
1
2
π2
π(πΊππ + πΊπ
2
)
+ *π2(π, π‘)+
Ο
inf
+ {λγππ(πβπ‘)
π1(π1, π2, π‘)}
π1,π2
inf
= 0#(6)
Where
π1(π1, π2, π‘) = β,ΞΌXΞ·1π1(π‘) + pΞΌYΞ·2π2(π‘)-
+
(Ξ³ + v0)ππ(πβπ‘)
2
,(π1ππ)2
+ p(π2ππ)2
+ 2pΟXΟYπ1π2-
π2(π, π‘) = ππππ(πβπ‘)(ΟΟπΊπ(Ξ³ + v1) β πΌ) +
1
2
(Ξ³ + v1)lΟ2
π2π(πβπ‘)
Theorem III.1 Let m=
ΞΌX(Ξ·1ππ
2βpΞ·2ΞΌY
2)
ππ₯
2ππ
2βπΞΌX
2ΞΌY
2 , n=
ΞΌY(Ξ·2ππ
2βΞ·1ΞΌX
2)
ππ₯
2ππ
2βπΞΌX
2ΞΌY
2 ,then there exist π‘1, π‘2π‘1
Μ, π‘2
Μ 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
π‘1 = π β
1
π
ln
π
Ξ³ + v0
, π‘2 = π β
1
π
ln
π
Ξ³ + v0
π‘1
Μ = π β
1
π
ln
ΞΌXΞ·1
(Ξ³ + v0)p(ππ
2 + ΞΌXΞΌY)
π‘2
Μ = π β
1
π
ln
ΞΌyΞ·2
(Ξ³ + v0)(ππ
2 + ΞΌXΞΌY)
When m β€ Ξ³(n β€ Ξ³),let π‘2 = π(π‘1 = π).When m > Ξ³(n > Ξ³),let π‘2 = 0(π‘1 = 0)(1)If π β€ n,then π1
β
β€ π2
β
οΌfor
all tΟ΅,0, T-οΌThe reinsurance strategy corresponding to the problem is(π1
β
, π2
β
) = {
(π1
Μ , π2
Μ)οΌ0 β€ π‘ β€ π‘2
(π1
Μ, 1
Μ)οΌπ‘2 β€ π‘ β€ π‘1
Μ
(1,1)οΌπ‘1 β€ π‘ β€ π
(2)If
n > m,then for alltΟ΅,0, T-οΌThe reinsurance strategy corresponding to the problem
is(π1
β
, π2
β
) = {
(π1
Μ , π2
Μ),0 β€ π‘ β€ π‘1
(1, π2
Μ), π‘1 β€ π‘ β€ π‘2
Μ
(1,1), π‘2
Μ β€ π‘ β€ π
. Where
π1
Μ =
ΞΌX(Ξ·1ππ
2
β pΞ·2ΞΌY
2)
(Ξ³ + v0)ππ(πβπ‘)(ππ₯
2ππ
2 β πΞΌX
2ΞΌY
2)
#(7)
π2
Μ =
ΞΌY(Ξ·2ππ
2
β Ξ·1ΞΌX
2)
(Ξ³ + v0)ππ(πβπ‘)(ππ₯
2ππ
2 β πΞΌX
2ΞΌY
2)
#(8)
π1
Μ =
ΞΌXΞ·1 β pΞΌXΞΌY(Ξ³ + v0)ππ(πβπ‘)
ππ
2(Ξ³ + v0)ππ(πβπ‘)p
#(9)
π2
Μ =
ΞΌyΞ·2 β ΞΌXΞΌY(Ξ³ + v0)ππ(πβπ‘)
ππ
2(Ξ³ + v0)ππ(πβπ‘)
#(10)
ProofοΌBy finding the first-order partial derivatives, second-order partial derivatives and second-order mixed
partial derivatives forπ1, the following system of equations and the Hessian array are obtained:
{
ππ1
ππ1
= βΞΌXΞ·1 + (Ξ³ + v0)ππ(πβπ‘)
,ππ
2
π1 + pΟXΟYπ2- = 0
ππ1
ππ2
= βΞΌYΞ·2 + (Ξ³ + v0)ππ(πβπ‘)
,ππ
2
π2 + ΟXΟYπ1- = 0
(11)
|
|
π2
π1
ππ1ππ1
π2
π1
ππ1ππ2
π2
π1
ππ2ππ1
π2
π1
ππ2ππ2
|
| = π4π(πβπ‘)
(Ξ³ + v0)2
|
βππ₯
2
(Ξ³ + v0) βpΟXΟY
βpΟXΟY βπππ¦
2
(Ξ³ + v0)
|
From the Hessian array positive definite it is known that π1(π1, π2, π‘) is a convex function and there exist
extreme value points; solving the system of equations (11) yields (7). (8).
ObviouslyοΌπ1
Μ γπ2
Μ are both increasing functions with respect to t, when π β€ n,0 β€ π‘ β€ π‘1 or n > mοΌ0 β€
π‘ β€ π‘2the solution as (7)(8)οΌAlso the values of π‘1 and π‘2 can be found. When π β€ nοΌπ‘2 β€ π‘ β€ π‘1
Μ οΌthen
(q1
β
, q2
β
) = (π1
Μ, 1),q1 β ,0,1-.When π > mοΌπ‘1 β€ π‘ β€ π‘2
Μ then (q1
β
, q2
β
) = (1, π1
Μ), q2 β ,0,1-,Separate solve
df1(t,q1,1)
dq1
= 0οΌ
df1(t,1,q2)
dq2
= 0 , then can get π1
Μ, π2
Μ as (9), (10) End.
Theorem III.2 The post-default insurer's optimal risky asset investment strategy is to
Οβ
=
Ξ± β ΟΟ(Ξ³ + v1)πΊ1
(Ξ³ + v1)ππ(πβπ‘)
#(12)
The expression of the optimal value function is:
V(t, x, y, l, 1) = β
1
Ξ³
exp*βΞ³ππ(πβπ‘)(t)x + G1(t)l + G2(t)+#(13)
π€ππππ Ο β Β±1, πΊ1 =
π1π2 β π1π2πβ
1
2
Ο2(π1βπ2)(Ξ³+v1)(1βΟ2)(πβπ‘)
π2 β π1πβ
1
2
Ο2(π1βπ2)(Ξ³+v1)(1βΟ2)(πβπ‘)
, #(14)
Ο = 1, πΊ1 =
Ξ±2
2(Ξ³ + v1)(Ξ±Ο + k)
(1 β πβ(Ξ±Ο+k)(πβπ‘)
), #(15)
7. Robust Optimal Reinsurance and Investment Problem with p-Thinning Dependent and Default ris
International Journal of Business Marketing and Management (IJBMM) Page 97
β ππ|
π1 β π2
π1 β π2π0.5π2(π1βπ2)(1βπ2)(Ξ³+v1)(πβπ‘)
|)οΌΟ β Β±1
Ξ±2
ππ
2(π + Ξ±Ο)(Ξ³ + v1)
(T β t) +
1
2
(
Ξ±
(k + Ξ±Ο)(Ξ³ + v1)
)2
ππ(1 β π(π+Ξ±Ο)(πβπ‘)
)οΌΟ = 1
Ξ±2
ππ
2(π β Ξ±Ο)(Ξ³ + v1)
(T β t) +
1
2
(
Ξ±
(k β Ξ±Ο)(Ξ³ + v1)
)2
ππ(1 β π(πβΞ±Ο)(πβπ‘)
)οΌΟ = β1, k β Ξ±Ο
ππ
,(Tβt)Ξ±-2
4(Ξ³+v1)
οΌΟ = β1οΌk = Ξ±Ο. 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 β€ t β€ Ο β§ T.Let the solution of the default prior value function
have the following form:
V(T, x, l, 0) = β
1
πΎ
ππ₯π{βπΎππ(πβπ‘)(π‘)π₯ + πΎ(π‘, π)}#(22)
Satisfying the boundary conditions V(T, x, l, 0)=V(x), K(T, l)=0, the HJB equation is transformed into:
ππ‘ + ,π(πΌπ β Ξ¦1βπ) + Ξ²Ξ΄(1 β Ξ) + λμX(ΞΈ1 + Ξ·1π1(π‘) β 1))
+Ξ»pΞΌY .ΞΈ2 + Ξ·2(π2(π‘) β 1)β(π1πΎ1)2 + (π2πΎ2)2 + 2Ο
Μπ1π2πΎ1πΎ2Ξ¦01 π
π₯
+
1
2
((π)2
π + Ξ»(π1ππ)2
+ Ξ»p(π2ππ)2
+ 2Ξ»pππππ)π
π₯π₯
+πππΟππ₯π + (k(Ο β l) β Ξ¦1ππβπ β Ξ¦2πβ1 β π2βπ))Vl +
1
2
Ο2
lVll
+π(ππΎΞ²(t)ΞΆπ»1(π‘)+πΎ(π‘,π)βG(π‘,π)
β 1)ππ
β
Ξ¦0
2
2v0
πΎ β
Ξ¦1
2
2v1
πΎ β
Ξ¦2
2
2v2
πΎ β
(Ξ¦3 ln Ξ¦3 β Ξ¦3 + 1)hp
(1 β h)
2v2
πΎ = 0
Similarly find the partial derivative of V:
{
ππ‘ = [Ξ³ππ(πβπ‘)
+ Ktβ]V, π
π₯ = βΞ³ππ(πβπ‘)
V
π
π₯π₯ = Ξ³2
π2π(πβπ‘)
ποΌππ₯π = βΞ³ππ(πβπ‘)
πΎππ
ππ = πΎππ, πππ = πΎπππ + πΎπ
2
π
Bringing the above expression into the HJB equation and fixing the reinsurance-investment strategy, the
minimum point of Ξ¦ is obtained according to the first-order condition as:
{
Ξ¦0
β
= v0ππ(πβπ‘)
β(π1πΎ1)2 + (π2πΎ2)2 + 2Ο
Μπ1π2πΎ1πΎ2
Ξ¦1
β
= v1ππ(πβπ‘)
πβπ, Ξ¦2
β
= βππβπKπv2
1
πΎ
Ξ¦3
β
= ππ₯π*
v3
πΎ
.πβπΎΞ²(t)ΞΆππ(πβπ‘)+πΊ1(π‘,π)βG(π‘,π)
β 1/+
#(23)
After bringing (23) into the HJB equation, by inverting the investment strategy we can obtain:
Οβ
=
Ξ± β ΟΟ(Ξ³ + v1)Kl
(Ξ³ + v1)ππ(πβπ‘)
, Ξ²β
=
ln
1
βΞ¦3
+ K(t, l) β G(t, l)
ΞΆΞ³ππ(πβπ‘)
and obviously the expressions for the reinsurance strategy before and after the bond default are the same, so that
π1(π‘, q1, q2) = π1(π‘, q1, q2) = β,ΞΌXΞ·1q1 + pΞΌYΞ·2q2-
+
1
2
,(q1ΟX)2
+ p(q2ΟY)2
+ pΟXΟYΞΌXΞΌYΞ³2
-(Ξ³ + v0)ππ(πβπ‘)
Bringing Ξ΅β
= (Οβ
, Ξ²β
, π1
β
, π2
β
) into the equation, after finishing, we get:
,βΞ³πππ(πβπ‘)
+ Ktβ- β ,λμX(ΞΈ1 β Ξ·1)
+Ξ»pΞΌY(ΞΈ2 β Ξ·2)-Ξ³ππ(πβπ‘)
+ k(Ο β l)Kl +
1
2
Ο2
l(Kll + Kl
2
)
βλγer(Tβt)
π1(q1
β
, q2
β
, t) β g2(Οβ
, t) β g3(Ξ²β
, 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
π2(Οβ
, t) = Οβ
πππ(πβπ‘)(ΟΟπΎπ(Ξ³ + v1) β πΌ) +
1
2
(Ξ³ + v1)lΟβ2
π2π(πβπ‘) (25)
π3(Ξ²β
, t) = β
(Ξ¦3 β 1)Ξ³hp
v3
β δβγer(Tβt)
#(26)
The derivative of equation (26) with respect to Ξ² οΌ
Ξ²β
=
ln
1
βΞ¦3
+ K(t, l) β G(t, l)
ΞΆΞ³ππ(πβπ‘)
#(27)
Bringing it into Ξ¦3
β
get :
hp
v3
Ξ¦3(π‘) ln Ξ¦3(π‘) + hp
Ξ¦3(π‘) β
πΏ
π
= 0. The equation has dimension one positive roots
Ξ¦3.
Let K(t, l)=K1(t)l + K2(t)οΌsatisfy the boundary conditions K1(T)=0,K2(T) = 0οΌbring it to HJB equation(24)οΌ
eliminating the effect of l on the equation yields two equations:
K1
β
β kπΎ1 +
1
2
Ο2
πΎ1
2
β
πΎ1 β πΊ1
ΞΆ
Ξ΄ β (ΟΟπΎ1 + Ξ±(Ξ΄ β r))Ξ±(Ξ΄ β r)
+
1
2
(ΟΟπΎ1 + Ξ±(Ξ΄ β r))
2
β (ΟΟπΎ1 + Ξ±(Ξ΄ β r))ΟΟπΎ1 = 0#(28)
K2
β
β ,λμX(ΞΈ1 β Ξ·1) + Ξ»pΞΌY(ΞΈ2 β Ξ·2)-Ξ³ππ(πβπ‘)
+ Ξ»pΟXΟYΞ³2
(ππ(πβπ‘)
)2
+kΟπΎ1 β
ln
1
βΞ¦3
+ πΎ2 β πΊ2
ΞΆ
Ξ΄ + (1 β
1
βΞ¦3
) hp
β f(t, π1
β
, π2
β) = 0#(29)
When Ο β Β±1,equation (28) is the first-order RICCATI equation thatοΌfrom the existence uniqueness of the
solution πΎ1 = πΊ1.Then we solve equation(29):let I(t)=πΎ2 β πΊ2, Satisfying the boundary condition I(T) = 0, then
using (29) and (21) we getοΌIβ = K2
β
β G2
β
=
Ξ΄
ΞΆ
I +
Ξ΄
ΞΆ
ln
1
βΞ¦3
+
Ξ³(Ξ¦3β1)
v3
hp
,
I = (ln
1
βΞ¦3
+ β β 1)π
β
Ξ΄
ΞΆ
(Tβt)
β ln
1
βΞ¦3
β β + 1.Thus οΌ
πΎ2 = (ln
1
βΞ¦3
+
Ξ³β(Ξ¦3 β 1)
v3
) π
β
Ξ΄
ΞΆ
(Tβt)
β ln
1
βΞ¦3
+
Ξ³β(Ξ¦3 β 1)
v3
+ πΊ2(30)
Theorem III.3 The optimal pre-default investment and bond investment strategies are:
Οβ
=
Ξ± β ΟΟ(Ξ³ + v1)Kl
(Ξ³ + v1)ππ(πβπ‘)
, π½β
=
π£3ln
1
ΞΞ¦3
+ ΞπΎ(Ξ¦3 β 1)(π
β
πΏ
π
(Tβt)
β 1)
π£3ππΎππ(πβπ‘)
The expression of the value function before default is:
π(π‘, π₯, π, 0) = β
1
πΎ
exp{βπΎππ(πβπ‘)
π₯ + K1(π‘)π+K2(π‘)+
Where K1(t) = G1(t)οΌas the formula (14)-(17)οΌK2(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/Ξ = 2.53, hQ
= 0.013, π = 0.52.The claim amounts for the first and second
categories of insurance respectively meet the parameters of Ξ»π = 1.5, Ξ»π = 1exponential distribution . If no
special statement is made, other model parameters are assumed as follows:οΌ t = 3, T = 10, π = 0.06, πΎ =
4οΌΞ·1 = 2, Ξ·2 = 3, p = 0.5, π0 = π1 = π3 = 1, Ο = 1, Ο = 0.16, π = 2, Ξ± = 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 πΎ 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 strategyΟβ
, 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 strategyΟβ
. 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
Ξ
on credit bonds, when the risk premium increases, investment in
credit bonds is increased. Figure.6 indicates that when the default loss rate π 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.
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