APPLICATIONS OF OPTION PRICING THEORY TO EQUITY VALUATION
Application of option pricing models to valuation

A few caveats on applying option pricing models

1. The underlying asset is not traded

2. The price of the asset follows a continuous process

3. The variance is known and does not change over the life of the option

4. Exercise is instantaneous

I. Valuing Equity as an option

The General Framework

Equity as a call option

Payoff to equity on liquidation

= V - D if V > D

= 0 if V

where,

V = Value of the firm

D = Face Value of the outstanding debt and other external claims

Payoff on exercise = S - K if S > K

= 0 if S

Payoff Diagram for Equity as a Call Option

Illustration 3: Application to valuation: A simple example

Model Parameters

The parameters of equity as a call option are as follows:

Value of the underlying asset = S = Value of the firm = $ 100 million

Exercise price = K = Face Value of outstanding debt = $ 80 million

Life of the option = t = Life of zero-coupon debt = 10 years

Variance in the value of the underlying asset = s2 = Variance in firm value = 0.16

Riskless rate = r = Treasury bond rate corresponding to option life = 10%

Valuing Equity as a Call Option

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 1.5994 N(d1) = 0.9451

d2 = 0.3345 N(d2) = 0.6310

Value of the call = 100 (0.9451) - 80 exp(-0.10)(10) (0.6310) = $75.94 million

Value of the outstanding debt = $100 - $75.94 = $24.06 million

Interest rate on debt = ($ 80 / $24.06)1/10 -1 = 12.77%


Implications of viewing equity as a call option

A. Valuing equity in a troubled firm

Illustration 4 : Value of a troubled firm

The parameters of equity as a call option are as follows:

Value of the underlying asset = S = Value of the firm = $ 50 million

Exercise price = K = Face Value of outstanding debt = $ 80 million

Life of the option = t = Life of zero-coupon debt = 10 years

Variance in the value of the underlying asset = s2 = Variance in firm value = 0.16

Riskless rate = r = Treasury bond rate corresponding to option life = 10%

Valuing Equity in a Troubled Firm

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 1.0515 N(d1) = 0.8534

d2 = -0.2135 N(d2) = 0.4155




Value of the call = 50 (0.8534) - 80 exp(-0.10)(10) (0.4155) = $30.44 million

Value of the bond= $50 - $30.44 = $19.56 million

B. The Conflict between bondholders and stockholders

Illustration 5: Effect on value of the conflict between stockholders and bondholders

Value of Equity = $75.94 million

Value of Debt = $24.06 million

Value of Firm == $100 million

Valuing Equity after the Project

Value of the underlying asset = S = Value of the firm = $ 100 million - $2 million = $ 98 million (The value of the firm is lowered because of the negative net present value project)

Exercise price = K = Face Value of outstanding debt = $ 80 million

Life of the option = t = Life of zero-coupon debt = 10 years

Variance in the value of the underlying asset = s2 = Variance in firm value = 0.25

Riskless rate = r = Treasury bond rate corresponding to option life = 10%

Based upon these inputs, the Black-Scholes model provides the following value for the equity and debt in this firm.

Value of Equity = $77.71

Value of Debt = $20.29

Value of Firm = $98.00

Illustration 6: Effects on equity of a conglomerate merger

You are provided information on two firms, which operate in unrelated businesses and hope to merge.

Firm A Firm B

Value of the firm $100 million $ 150 million


Face Value of Debt $ 80 million $ 50 million (Zero-coupon debt)

Maturity of debt 10 years 10 years


Std. Dev. in firm value 40 % 50 %

Correlation between firm

cashflows 0.4

The ten-year bond rate is 10%.

Variance in combined firm value = w12 s12 + w22 s22 + 2 w1 w2 r12 s1 s2

= (0.4)2 (0.16) + (0.6)2 (0.25) + 2 (0.4) (0.6) (0.4) (0.4) (0.5)

= 0.154

Valuing the Combined Firm

The values of equity and debt in the individual firms and the combined firm can then be estimated using the option pricing model:

Firm A Firm B Combined firm

Value of equity in the firm $75.94 $134.47 $ 207.43

Value of debt in the firm $24.06 $ 15.53 $ 42.57

Value of the firm $100.00 $150.00 $ 250.00

Obtaining option pricing inputs - Some real world problems

The examples that have been used to illustrate the use of option pricing theory to value equity have made some simplifying assumptions. Among them are the following:

(1) There were only two claim holders in the firm - debt and equity.

(2) There is only one issue of debt outstanding and it can be retired at face value.

(3) The debt has a zero coupon and no special features (convertibility, put clauses etc.)

(4) The value of the firm and the variance in that value can be estimated.

Applicability in valuation

Input
Estimation Process
Value of the Firm
  • Cumulate market values of equity and debt (or)
  • Value the firm using FCFF and WACC (or)
  • Use cumulated market value of assets, if traded.
Variance in Firm Value
  • If stocks and bonds are traded,

s2firm = we2 se2 + wd2 sd2 + 2 we wd red sesd

where se2 = variance in the stock price we = MV weight of Equity

sd2 = the variance in the bond price wd = MV weight of debt

  • If not traded, use variances of similarly rated bonds.
  • Use average firm value variance from the industry in which company operates.
Maturity of the Debt
  • Face value weighted duration of bonds outstanding (or)
  • If not available, use weighted maturity


Illustration 7: Valuing Equity as an option - The example of an airline

North America $ 400 million

Europe $ 500 million

South America $ 100 million

Maturity Face Value Coupon Duration

20 year debt $ 100 mil 11% 14.1 years

15 year debt $ 100 mil 12% 10.2 years

10 year debt $ 200 mil 12% 7.5 years

1 year debt $ 800 mil 12.5% 1 year

Valuing Equity in the Airline

Step 1: Estimate the value of the firm = Sum of the value of its assets = 400 + 500 + 100 = 1,000 million

Step 2: Estimate the average duration of the debt outstanding = (100/1200) * 14.1 + (100/1200) * 10.2 + (200/1200) * 7.5 + (800/1200) * 1 = 3.9417 years

Step 3: Estimate the face value of debt outstanding = 100 + 100 + 200 + 800 = 1,200 million

Step 4: Estimate the variance in the value of the firm = Weighted average of the variances in stock and bond prices. =

Variance of the firm = (E/(D+E))2 se2 + (D/(D+E))2 sd2 + 2 (E/(D+E)) (D/(D+E)) red sesd

= (.1)2 (.25)2 + (.9)2 (.10)2 + 2 (.1)(.9)(.3) (.25)(.10) = 0.010075


Step 5: Value equity as an option

d1 = 0.7671 N(d1) = 0.7784

d2 = 0.5678 N(d2) = 0.7148

Value of the call = 1000 (0.7784) - 1200 exp(-0.08)(3.9417) (0.7148) = $ 152.63 million




Illustration 8: Valuing Equity as an option - Cablevision Systems

Debt Type Face Value Duration

Short term Debt $ 865 mil 0.5 years

Bank Debt $ 480 mil 3.0 years

Senior Debt $ 832 mil 6.0 years

Senior Subordinated $ 823 mil 8.5 years

Total $ 3000 mil 4.62 years



Cost of Capital in high growth period = 16.03% (0.2986) + 10% (1 - 0.36) (0.7014) = 9.27%

Cost of Capital in terminal period = 13.55% (0.50) + 8.50% (1 - 0.36) (0.50) = 9.34%

1
2
3
4
5
6
7
8
9
10
Term. Year
Revenues
$954.4
$1,088.0
$1,240.3
$1,414.0
$1,611.9
$1,808.6
$1,996.7
$2,168.4
$2,315.8
$2,431.6
$2,553.26
- COGS
$658.5
$739.86
$831.03
$933.24
$1,047.7
$1,175.6
$1,297.1
$1,409.4
$1,505.3
$1,580.5
$1,659.62
- Depreciation
$253.0
$278.30
$306.13
$336.74
$370.42
$388.94
$408.39
$428.80
$450.24
$472.76
$496.39
EBIT
$42.87
$69.87
$103.19
$144.02
$193.77
$244.08
$290.46
$330.15
$360.31
$378.33
$397.25
- EBIT*t
$15.43
$25.15
$37.15
$51.85
$69.76
$87.87
$104.57
$118.85
$129.71
$136.20
$143.01
EBIT (1-t)
$27.43
$44.72
$66.04
$92.17
$124.01
$156.21
$185.90
$211.29
$230.60
$242.13
$254.24
+ Depreciation
$253.0
$278.30
$306.13
$336.74
$370.42
$388.94
$408.39
$428.80
$450.24
$472.76
$496.39
-Capital Spending
$275.0
$302.50
$332.75
$366.03
$402.63
$422.76
$443.90
$466.09
$489.40
$513.87
$496.39
- Æ Wking Capital
$5.86
$6.68
$7.62
$8.68
$9.90
$9.83
$9.40
$8.59
$7.37
$5.79
$6.08
Free CF to Firm
($0.43)
$13.83
$31.80
$54.21
$81.90
$112.56
$140.98
$165.42
$184.08
$195.23
$248.16
                       

The stock and bond price variance are first annualized:

Annualized variance in stock price = 0.0133 * 12 = 0.16 Standard deviation = 0.40

Annualized variance in bond price = 0.0012 * 12 = 0.0144 Standard deviation = 0.12

Annualized variance in firm value

= (0.30)2 (0.16) + (0.70)2 (0.0.0144) + 2 (0.3) (0.7)(0.25)(0.40)(0.12)= 0.02637668

The parameters of equity as a call option are as follows:

Value of the underlying asset = S = Value of the firm = $ 2871 million

Exercise price = K = Face Value of outstanding debt = $ 3000 million

Life of the option = t = Weighted average duration of debt = 4.62 years

Variance in the value of the underlying asset = s2 = Variance in firm value = 0.0264

Riskless rate = r = Treasury bond rate corresponding to option life = 7%

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 0.9910 N(d1) = 0.8391

d2 = 0.6419 N(d2) = 0.7391

Value of the call = 2871 (0.8391) - 3000 exp(-0.07)(4.62) (0.7395) = $ 817 million



Cablevision's equity was trading at $1100 million in March 1995.

II. Valuing Natural Resource Options/ Firms

The General Framework

Payoff on natural resource investment = V - X if V > X

= 0 if V

Payoff on a Natural Resource Investment

Obtaining the inputs for valuing natural resource options

Input
Estimation Process
1. Value of Available Reserves of the Resource
  • Expert estimates (Geologists for oil..); The present value of the after-tax cash flows from the resource are then estimated.
2. Cost of Developing Reserve (Strike Price)
  • Past costs and the specifics of the investment
3. Time to Expiration
  • Relinqushment Period: if asset has to be relinquished at a point in time.
  • Time to exhaust inventory - based upon inventory and capacity output.
4. Variance in value of underlying asset
  • based upon variability of the price of the resources and variability of available reserves.
5. Net Production Revenue (Dividend Yield)
  • Net production revenue every year as percent of market value.
6. Development Lag
  • Calculate present value of reserve based upon the lag.


Illustration 9 : Application to valuation: A gold mine

Inputs for the Option Pricing Model

Value of the underlying asset = Present Value of expected gold sales (@ 50,000 ounces a year) = (50,000 * 350) * (1- (1.0320/1.1020))/(.10-.03) - (50,000*250)* (1- (1.0420/1.1020))/(.10-.04) = $ 42.40 million

Exercise price = PV of Cost of opening mine = $40 million

Variance in ln(gold price) = 0.04

Time to expiration on the option = 20 years

Riskless interest rate = 9%

Dividend Yield = Loss in production for each year of delay = 1 / 20 = 5%

(Note: It will take twenty years to empty the mine, and the firm owns the rights for twenty years. Every year of delay implies a loss of one year of production.)

Valuing the Option

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 1.4069 N(d1) = 0.9202

d2 = 0.5124 N(d2) = 0.6958

Call Value= 42.40 exp(-0.05)(20) (0.9202) -40 (exp(-0.09)(20) (0.6958)= $ 9.75 million

The value of the mine as an option is $ 9.75 million, in contrast to the static capital budgeting analysis which would have yielded a net present value of $ 2.40 million ($42.40 million - $ 40 million). The additional value accrues directly from the mine's option characteristics.

Illustration 10: Valuing an oil reserve

Inputs to the Black-Scholes Model

Given this information, the inputs to the Black-Scholes can be estimated as follows:

Current Value of the asset = S = Value of the developed reserve discounted back the length of the development lag at the dividend yield = $12 * 50 /(1.05)2 = $ 544.22

(If development is started today, the oil will not be available for sale until two years from now. The estimated opportunity cost of this delay is the lost production revenue over the delay period. Hence, the discounting of the reserve back at the dividend yield)

Exercise Price = Present Value of development cost = $12 * 50 = $600 million

Time to expiration on the option = 20 years

Variance in the value of the underlying asset = 0.03

Riskless rate =8%

Dividend Yield = Net production revenue / Value of reserve = 5%

Valuing the Option

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 1.0359 N(d1) = 0.8498

d2 = 0.2613 N(d2) = 0.6030

Call Value= 544 .22 exp(-0.05)(20) (0.8498) -600 (exp(-0.08)(20) (0.6030)= $ 97.08 million

This oil reserve, though not viable at current prices, still is a valuable property because of its potential to create value if oil prices go up.

Extending the option pricing approach to value natural resource firms

Inputs to the Black-Scholes Model

Input to model Corresponding input for valuing natural resource firm

Value of underlying asset Value of cumulated estimated reserves of the resource owned by the firm, discounted back at the dividend yield for the development lag.

Exercise Price Estimated cumulated cost of developing estimated reserves

Time to expiration on option Average relinquishment period across all reserves owned by firm (if known) or estimate of when reserves will be exhausted, given current production rates.

Riskless rate Riskless rate corresponding to life of the option

Variance in value of asset Variance in the price of the natural resource

Dividend yield Estimated annual net production revenue as percentage of value of the reserve.

Illustration 11: Valuing an oil company - Gulf Oil in 1984

Valuing the Option

Value of underlying asset = Value of estimated reserves discounted back for period of development lag= 3038 * ($ 22.38 - $7) / 1.052 = $42,380.44

Exercise price = Estimated development cost of reserves = 3038 * $10 = $30,380 million

Time to expiration = Average length of relinquishment option = 12 years

Variance in value of asset = Variance in oil prices = 0.03

Riskless interest rate = 9%

Dividend yield = Net production revenue/ Value of developed reserves = 5%

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 1.6548 N(d1) = 0.9510

d2 = 1.0548 N(d2) = 0.8542

Call Value= 42,380.44 exp(-0.05)(12) (0.9510) -30,380 (exp(-0.09)(12) (0.8542)= $ 13,306 million

Valuing Gulf Oil

Value of already developed reserves = 915 (1 - 1.125-10)/.125 = $5065.83

Adding the value of the developed and undeveloped reserves of Gulf Oil provides the value of the firm.

Value of undeveloped reserves = $ 13,306 million

Value of production in place = $ 5,066 million

Total value of firm = $ 18,372 million

Less Outstanding Debt = $ 9,900 million

Value of Equity = $ 8,472 million

Value per share = $ 8,472/165.3 = $51.25

This analysis would suggest that Gulf Oil was overvalued at $70 per share.

III. Valuing product patents as options

The General Framework

Payoff from owning a product patent = V - I if V> I

= 0 if V



Obtaining the inputs for option valuation
Input
Estimation Process
1. Value of the Underlying Asset
  • Present Value of Cash Inflows from taking project now
  • This will be noisy, but that adds value.
2. Variance in value of underlying asset
  • Variance in cash flows of similar assets or firms
  • Variance in present value from capital budgeting simulation.
3. Exercise Price on Option
  • Option is exercised when investment is made.
  • Cost of making investment on the project; assumed to be constant in present value dollars.
4. Expiration of the Option
  • Life of the patent
5. Dividend Yield
  • Cost of delay
  • Each year of delay translates into one less year of value-creating cashflows



Illustration 12: Valuing a product option

Valuing the Option

The inputs to the option pricing model are as follows:

Value of the underlying asset = Present value of inflows (current) = $1,000 million

Exercise price = Present value of cost of developing product = $1,500 million

Time to expiration = Life of the patent = 20 years

Variance in value of underlying asset = Variance in PV of inflows = 0.03

Riskless rate = 10%

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 1.1548 N(d1) = 0.8759

d2 = 0.3802 N(d2) = 0.6481

Call Value= 1000 exp(-0.05)(20) (0.8759) -1500 (exp(-0.10)(20) (0.6481)= $ 190.66 million

Illustration 13: Valuing a firm with only product options

Inputs to the Option Pricing Model

The inputs to the option pricing model are as follows:

Value of underlying asset = Present value of expected cashflows = $ 500 million

Exercise price = Present value of cost of developing product for commercial use = $400 mil

Time to expiration on the option = Time to expiration on patent rights = 25 years

Variance in value of underlying asset = 0.20

Riskless rate = 7%

Dividend yield = Expected annual cashflow / PV of cash inflows = 4%

Based upon these inputs, the Black-Scholes model provides the following value for the call:

d1 = 1.5532 N(d1) = 0.9398

d2 = -0.6828 N(d2) = 0.2474

Call Value= 500 exp(-0.04)(25) (0.9398) - 400 (exp(-0.07)(25) (0.2474)= $ 155.66 million

Valuing Biogen

 

Value of Existing Products = $ 12.14

 

Present Value of Cash Flows from Introducing the Drug Now = S = $ 3.422 billion

Present Value of Cost of Developing Drug for Commercial Use = K = $ 2.875 billion


Patent Life = t = 17 years Riskless Rate = r = 6.7% (17-year T.Bond rate)

Variance in Expected Present Values =s2 = 0.224 (Industry average firm variance for bio-tech firms)

Expected Cost of Delay = y = 1/17 = 5.89%

d1 = 1.1362 N(d1) = 0.8720

d2 = -0.8512 N(d2) = 0.2076

Call Value= 3,422 exp(-0.0589)(17) (0.8720) - 2,875 (exp(-0.067)(17) (0.2076)= $ 907 million



Call Value per Share from Avonex = $ 907 million/35.5 million = $ 25.55

Biogen Value Per Share = Value of Existing Assets + Value of Patent = $ 12.14 + $ 25.55 = $ 37.69