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The Black-Scholes European Call Option Formula Corrected Using the Gram-Charlier Expansion

skewness
-1
kurtosis
4
volatility
0.15
time to expiry
0.25
Column[Transpose[{
Black-Scholes
,
Corrected Black-Scholes
}{
}], ]
Transpose
:The first two levels of {{
Black-Scholes
,
Corrected Black-Scholes
},{
}} cannot be transposed.
It has long been well-known that the BlackScholes model frequently misprices deep in-the-money and out-of-the-money options. A large part of the problem seems to lie in the normality assumptions of the BlackScholes model. Empirical evidence shows that actual stock prices and stock returns have a distribution that is usually skewed and has a larger kurtosis than the log-normal distribution. There are a number of approaches that attempt to correct this problem. Here we illustrate an approach based on using the Edgeworth (or GramChalier) series, which allows one to expand a given probability density function in terms of the probability density function of the normal distribution and cumulants of the given PDF. Using a finite truncation of this series instead of the original PDF we obtain a formula for option prices with correction terms for nonzero values of skewness and excess kurtosis (kurtosis -3).
The plot shows the BlackScholes and the corrected BlackScholes values of the European call option on a stock with initial price of 100 that pays no dividend against the "percentage moneyness" of the option defined as
S-Kexp(-rt)
Kexp(-rt)
100%
, where
S
is the initial price of the stock,
K
is the strike price,
t
is the time to expiry, and
r
is the interest rate (which in this Demonstration is taken to be 0).
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