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In 1973, Fischer Black and
Myron Scholes published their groundbreaking paper
the pricing of options and corporate liabilities.
Not only did this specify the first successful options pricing formula, but it
also described a general framework for pricing other
derivative instruments. That paper
launched the field of financial engineering.
Black and Scholes had a very hard time getting that paper published. Eventually,
it took the intersession of Eugene Fama and Merton Miller to get it accepted by
the Journal of Political Economy. In the mean time, Black and Scholes had
published in the Journal of Finance a more accessible (1972)
paper that cited the as-yet unpublished (1973) option pricing formula in an
empirical analysis of current options trading.
The
Black-Scholes (1973)
option pricing formula prices
European put
or call options on a
stock that does not pay a
dividend or make other
distributions. The formula assumes the underlying stock price follows a
geometric Brownian motion with constant
volatility. It is historically
significant as the original option pricing formula published by Black
and Scholes in their landmark (1973) paper.
Values for a call price
c or put price p are:
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[1] |
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[2] |
where:
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[3] |
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[4] |
Here, log denotes the natural logarithm, and:
s = the price of the
underlying stock
x = the
strike price
r = the
continuously compounded
risk free interest rate
t = the time in years until the
expiration of the
option
σ = the
implied volatility for
the underlying stock
Φ = the
standard normal
cumulative distribution function.
Consider a European call option on 100
shares of non-dividend-paying
stock ABC. The option is struck at USD 55 and expires in .34 years. ABC is
trading at USD 56.25 and has 28% (that is .28) implied volatility. The
continuously compounded risk free interest rate is .0285. Applying formula [1],
the option's market value per share of ABC is USD 4.56. Since the call is for
100 shares, its total value is USD 456. Of this, USD 125 is
intrinsic value, and USD 331 is
time value.
The
Greeksdelta,
gamma,
vega,
theta and rhofor a call are:
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delta =
Φ(d1) |
[5] |
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gamma =
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[6] |
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vega =
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[7] |
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theta =
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[8] |
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[9] |
where
denotes the standard
normal probability density function. For a put, the Greeks are:
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delta =
Φ(d1) 1 |
[10] |
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gamma =
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[11] |
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vega =
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[12] |
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theta =
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[13] |
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[14] |
Note that gamma formulas [6] and [11]are identical for puts
and calls, as are vega formulas [7] and [12].
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To learn about the historical origins
of the Black-Scholes formula, see Mehrling (2005)
or Bernstein (1993). Haug (1997)
is a handy encyclopedia of published option pricing formulas,
including Black-Scholes. Natenberg (1994)
is an excellent introduction to options trading. Cox and
Rubinstein (1985)
is a classic. Pretty much everyone who works with options has read
it at some point. Hull (2005)
is a standard introduction to financial engineering that covers
the derivation of Black-Scholes in detail.
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Black,
Fischer and Myron S. Scholes (1972) The valuation of option
contracts and a test of market efficiency, Journal of Finance,
27 (2), 399418.
Black,
Fischer and Myron S. Scholes (1973). The pricing of options and
corporate liabilities, Journal of Political Economy, 81 (3), 637-654.
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