
P1: JYS
app04 JWBK378-Fletcher April 24, 2009 8:20 Printer: Yet to come
Appendix D
Pickup Value Regression
The seminal paper by Longstaff and Schwartz [15], on estimating the early exercise premium,
uses regressions of the holding value, i.e. the value of holding on to the option. In this short
appendix we develop a simple alternative regression scheme for determining the early exercise
premium of a callable structure when pricing using Monte-Carlo.
Consider times T
1
< T
2
<...<T
N
and denote B
t
as the numeraire at time t. The holding
value H
n−1
(T
n−1
) at time T
n−1
is given by the relation below
HV
n−1
(T
n−1
) = B
T
n−1
E
B
−1
T
n
max(IEV
n
(T
n
), HV
n
(T
n
))|F
T
n−1
= B
T
n−1
E
B
−1
T
n
(IEV
n
(T
n
) −HV
n
(T
n
))
+
|F
T
n−1
+ B
T
n−1
E
B
−1
T
n
HV
n
(T
n
)|F
T
n−1
(D.1)
where IEV
n
(T
n
) denotes the immediate exercise values at time T
n
. Setting HV
N
(T
N
) = 0 and
using the above recursion relation, we obtain
HV
n−1
(T
n−1
) = B
T
n−1
N
m=n
E
B
−1
T
m
(IEV
m
(T
m
) −HV
m
(T
m
))
+
|F
T
n−1
(D.2)
Let’s denote the exercise region at time T
n
by R
n
,
R
n
=
{
ω ∈ : H
n
(T
n
,ω) ≤ IEV
n
(T
n
,ω)
}
(D.3)
=
{
ω ∈ : IEV
n
(T
n
,ω) − H
n
(T
n
,ω) ≥ 0
}
(D.4)
The stopping time is then (T
N+1
denoting no exercise)
τ (ω) = min
{
T
n
, n ≥ 1|ω ∈ R
n
}
∧ N +1(D.5)
The pickup value PKV
n
(T
n
) at time T
n
is defined by
PKV
n
(T
n
):= IEV
n
(T
n
) −HV
n
(T
n
)(D.6)
At each time T
n
we approximate the the pickup value by the following sum:
G
n
(T
n
,ω) =
M
k=1
α
k
(T
n
)X
k
x
1
(T
n
,ω), x
2
(T
n
,ω),...,x
p
(T
n
,ω)
(D.7)
where {X
1
(...), X
2
(...), ..., X
m
(...)} are the basis ...