Economics of Finance Tutorial 4 solution
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Economics of Finance
Tutorial 4 solution
1. Consider a three period binomial time-state model in which there are two securities, a bond and a stock. The payments made by these securities in each state are shown in the trees below:
Stock
g
1.00 ↘(╱)0(0)
<
<
0.64
bb
Bond
gg
1.21
一
一
gb
1.21
1.21
bg
<
<
1.21
bb
(i) Write down the payment matrix, Q, and corresponding price vector, pS , derived from the following elemental payment combinations:
B0: Buy a Bond at period 0, sell it at the end of the next period;
S0: Buy a Stock at period 0, sell it at the end of the next period;
Bg: At period 1, if the state is g, buy a Bond, sell it at the end of the next period; Sg: At period 1, if the state is g, buy a Stock, sell it at the end of the next period; Bb: At period 1, if the state is b, buy a Bond, sell it at the end of the next period; Sb: At period 1, if the state is b, buy a Stock, sell it at the end of the next period.
Solution
The Q matrix derived from the elemental payment combinations B0, S0, Bg, Sg, Bb, Sb is as
follows:
╱ 一01 一01 0一1 0一1、
Q = 0 0 1.1 0.8 0 0
. 0 0 0 0 1.1 1.5.
The corresponding securities price vector is
pS = ╱ 1 1 0 0 0 0、.
(ii) Compute the atomic security prices (i.e., the price of one dollar in each of the six future time- states: g, b, gg, gb, bg, bb). Write down the formula you used to derive the atomic security price vector.
Solution
The atomic security price vector can be derived from the Q matrix and its corresponding pS vector: patom = pS.Q-1 = ╱0.389 61 0.519 48 0.151 80 0.202 40 0.202 40 0.269 86、
(iii) Write down the payment matrix, Q, and corresponding price vector, pS , derived from the following elemental payment combinations:
B0: Buy a Bond at period 0, sell it at the end of the next period;
S0: Buy a Stock at period 0, sell it at the end of the next period;
Bb: At period 1, if the state is b, buy a Bond, sell it at the end of the next period; Sb: At period 1, if the state is b, buy a Stock, sell it at the end of the next period.
B02: Buy a Bond at period 0, sell it at the end of period 2;
S02: Buy a Stock at period 0, sell it at the end of period 2;
Solution
The Q matrix derived from the elemental payment combinations B0, S0, Bb, Sb, B02, S02 is as
follows:
╱ 0一1 0一 、
Q = 0 0 0 0 1.21 1.20
. 0 0 1.1 1.5 1.21 1.20.
The corresponding securities price vector is
pS = ╱ 1 1 0 0 1 1、.
(iv) Verify the atomic security prices computed using the payment matrix Q in part (iii) is the same as the one found using the payment matrix Q in part (i).
Solution
The atomic security price vector derived from the Q matrix from part (iii) is the same as the vector derived from the Q matrix in part (i). They are different representations of the same market.
(v) Suppose an investor wants to obtain the following time-state payments: c = ╱0 10 20 20 30 40、\ .
The vector of payment combination holdings, n, is calculated as follows: n = Q-1 c. Calculate n for both the Q matrices considered in (i) and (iii) above.
Solution
Using the elemental payment combinations from part (i) we get:
n = Q-1 c = 0 ( 0 |
1.5 0.8 0 0 0 0 |
一1 0 1.1 1.1 0 0 |
一1 0 1.5 0.8 0 0 |
0 一1 0 0 1.1 1.1 |
0一1、 ╱ 10(0)、 ╱ 6一、 0 .(.) .(.) 20 .(.) .(.) 18. 182 .(.) 0 .(.) .(.) 20 .(.) = .(.) 0 .(.) 0.8. (40. (一14. 286. |
Using the elemental payment combinations from part (ii) we get:
n = Q-1 c = 0 ( 0 |
1.5 0.8 0 0 0 0 |
0 一1 0 0 1.1 1.1 |
0 一1 0 0 1.5 0.8 |
0 0 1.21 1.21 1.21 1.21 |
0(0) 、 ╱ 10(0)、 ╱ 4一、 2.25 .(.) .(.) 20 .(.) .(.) 28. 571 .(.) 1.20 .(.) .(.) 20 .(.) = .(.) 一14. 286 .(.) 0.64. (40. ( 0 . |
(vi) Take each vector n from part (v) and calculate how much of the bond and stock the investor must buy or sell in aggregate in each state in period 1 to implement this dynamic strategy? Show your workings, and verify that both n vectors are describing the same overall strategy.
Solution
Taking the elemental payment combinations from part (i), the dynamic strategy is implemented as follows:
Period 0: |
Buy 63. 839 of Bond (row 1 of vector n) Sell 34. 694 of Stock (row 2 of vector n) |
Period 1 (good) . Sell previously purchased Bonds for 63. 839 × 1.1 = 70. 223 |
. Buy previously sold Stocks for 34 . 694 × 1.5 = 52 . 041 |
. Buy 18. 182 worth of Bond (row 3 of vector n) |
. Sell/Buy 0 of Stock (row 4 of vector n) |
Overall change in holdings after state g: |
. Sell 52. 041 worth of Bonds (一70. 223 + 18. 182 = 一52. 041) |
. Buy 52. 041 worth of Stocks |
Cash flow in state g: |
一52. 041 + 52. 041 = 0 (row 1 of vector c) |
Period 1 (bad) . Sell previously purchased Bonds for 63 . 839 × 1.1 = 70. 223 |
. Buy previously sold Stocks for 34 . 694 × 0.8 = 27 . 755 |
. Buy 46. 753 worth of Bond (row 5 of vector n) |
. Sell 14. 286 worth of Stock (row 6 of vector n) |
Overall change in holdings after state b: |
. Sell 23. 47 worth of Bonds (一70. 223 + 46. 753 = 一23. 47) |
. Buy 13. 469 worth of Stocks (27 . 755 一 14. 286 = 13. 469) |
Cash flow in state b: |
23. 47 一 13. 469 = 10. 00 (row 2 of vector c) |
2022-07-16