Page 48 - 36-1
P. 48
Ambiguity Increases and Insurance Deductibles
∗ ∗
� � � �
∗
�
∗
∗
�
�
�
∗
∗
∗
� �
−
− � − − )) �� , ) − , )��1− , )�� − − )) �� , ) − , )��1− , )�
� �
�
�
�
�
�
�
�
�
�
�
� �
− � , ) − , )��1 − , )�� − , )��
� �
∗
�
∗
�
�
∗
�
∗
− � , ) − , )��1
� � � � � � � � � �
� �
�
�
�
�
=− ��
=− �� − � − � − � − �
��
��
� �
= >0, = >0,
�
�
��
��
ct
which contradicts Equation (E3). s Equation (E3).
ntradi
which co
�
Next, we prove that Condition (E4) holds for all , 1] and 0, ] through the , 1] and 0, ] through the
�
∗
∗
Next, we prove that Condition (E4) holds for all
� � � �
following procedure. Let ng procedure. Let
foll
owi
, ) = � , ) − , )� �1 − , )� , ) − , )� �1 − , )�
∗
∗
∗
�
�
�
� �
∗
�
, ) = �
� � � � � �� � � �
−� , ) − , )� �1− , )�. , ) − , )� �1− , )�.
�
∗
∗
∗
�
∗
�
�
� �
−�
� � � � � �� � � �
Given that = 0, ], , ) is a quadratic function of 0, 1]. Then, by letting 0, ], , ) is a quadratic function of 0, 1]. Then, by letting
∗
∗
Given that =
�
�
� �
�
�
c
w
ma
n
i
,
a
loc
c
s
a
a
�� � � ,�) �� � � ,�)
i
nd
h
e
t
w
a
l
h
=0, we can find an ) at which , )) is a local maximum or minimum. ximum or minimum.
a
f
n
i
∗
∗
∗
∗
,
))
=0
)
�� �� � �� � � �
�
�
� � � � ,�)
cannot be determined, we consider all possible cases. all possible cases.
B
e
Because the sign of cause the sign of � � � � ,�) c ann ot be d eterm i ned , we consi der
�� � �� �
Considering the interval in which ) lies and , )) is a local maximum or ) lies and , )) is a local maximum or
∗
∗
∗
∗
Considering the interval in which
�
� �
�
�
�
minimum, we obtain the determining conditions under which ≤ for all >0, <0, ≤ for all >0, <0,
��
�
�∗
∗
��
∗
∗
minimum, we obtain the determining conditions under which
� � � �
and , 1], as follows. , 1], as follows.
�
�
and
� �
� � � � � ,�)
�
Case 1. Case 1. ∗ ≤0 � a t ∗ �
≤0 at ) 0, ]. ) 0, ].
� � � � ,�)
�� � �� � � � � �
Since , )) is a local maximum when ) lies in 0, ], the condition , ) ≤ 0 , )) is a local maximum when ) lies in 0, ], the condition , ) ≤ 0
�
�
∗
∗
∗
∗
Since
�
�
�
�
�
� � � � �
for all , 1] is equivalent to requiring , + ) ≤ 0 for 0< ≤ . , 1] is equivalent to requiring , + ) ≤ 0 for 0< ≤ .
�
�
�
�
�
�
for all
� � � � � � � � �
�
≥0 at ) 0, ]. ) 0, ].
Case 2. � � � � ,�) Case 2. � � � � ,�) ≥0 � a t ∗ �
∗
�� � �� � � � � �
Since , )) is a local minimum when ) lies in 0, ], the condition , ) ≤ 0 , )) is a local minimum when ) lies in 0, ], the condition , ) ≤ 0
�
�
∗
∗
∗
∗
Since
�
�
�
�
�
� � � � �
�
�
for all , 1] is equivalent to requiring , 1)≤0. , 1] is equivalent to requiring , 1)≤0.
for all
� � � �
�
� � � � � ,�)
� � � � ,�)
≤0 at ) , 1]. ) , 1].
Case 3. Case 3. ∗ ≤0 a t ∗ �
�
�� � �� � � � � �
�
Since , )) is a local maximum when ) , 1], the condition , ) ≤ 0 for , )) is a local maximum when ) , 1], the condition , ) ≤ 0 for
�
∗
∗
∗
∗
Since
�
�
�
�
�
� � � � �
all , 1] is equivalent to requiring , )) ≤ 0. , 1] is equivalent to requiring , )) ≤ 0.
�
�
∗
∗
all
� � � � � �
�
�
Case 4. � � � � ,�) Case 4. � � � � ,�) ≥0 a t ∗ �
≥0 at ) , 1). ) , 1).
�
∗
�� � �� � � � � �
Since , )) is a local minimum when ) lies in , 1), the condition , ) ≤ 0 , )) is a local minimum when ) lies in , 1), the condition , ) ≤ 0
�
�
∗
∗
∗
∗
Since
�
�
�
�
�
� � � � �
for all , 1] is equivalent to requiring , + ) ≤ 0 and , 1)≤0, where 0< ≤ . , 1] is equivalent to requiring , + ) ≤ 0 and , 1)≤0, where 0< ≤ .
�
�
�
�
�
�
for all
� � � � � � � � � �
�
� � � � � ,�)
≥0 at )=1. ≥0 at )=1.
� � � � ,�)
Case 5. Case 5. ∗ ∗
�� � �� � � �
40

