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Published byRosa Stone Modified over 9 years ago
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Known dividend to be paid before option expiration ◦ Dividend has already been announced or stock pays regular dividends ◦ Option should be priced on S 0 – PV(dividends anticipated before t) = S 0 – Div * exp(-r*time dividend paid) ◦ Example: Coca-Cola pays relatively stable quarterly dividend around $0.31 per share on November 29 th each year. Assuming it is November 14, use S 0 – 0.31* exp(-r*15/365) for current stock price in Black-Scholes model for February option.
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Continuous Dividend Payments ◦ Index funds on basket of stocks (e.g. S&P 500 index): the many stocks pay out their dividends throughout the year ◦ Merton Model: Assume continuous dividend yield k
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Strategies if anticipate that stock price will rise over period t ◦ Purchase calls ◦ Purchase stock ◦ Purchase stock and put to insure portfolio ◦ Write put Strategies if anticipate that stock price will decline over period t ◦ Purchase puts ◦ Write calls Covered call: purchase stock
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Want to guarantee that t periods from now you will have at least I*z ◦ z is a number generally between 0 and 1that guarantees a minimum value ◦ Want to invest in Stock with price S 0 and put on stock with exercise price X ◦ A package of share + put costs S 0 + P(S 0,X) ◦ Buy packages where =I/(S 0 + P(S 0,X)) Minimum $ return = X which should be set to I*z Pick X to guarantee that S 0 + P(S 0,X)=X/z
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Most financial models of stock prices assume that the stock’s price follows a lognormal distribution. (The logarithm of the stock’s price is normally distributed) This implies the following relationship: P t = P 0 * exp[(μ-.5*σ 2 )*t + σ*Z*t.5 ]
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◦ P 0 = Current price of stock ◦ t = Number of years in future ◦ P t = Price of stock at time t Random Variable!! ◦ Z = A standard normal random variable with mean 0 and standard deviation 1 Random Variable!! ◦ μ = Mean percentage growth rate of stock per year expressed as a decimal ◦ σ = Standard deviation of the growth rate of stock per year expressed as a decimal. Also referred to as the annual volatility.
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Option price is the expected discounted value of the cash flows from an option on a stock having the same volatility as the stock on which the option is written and growing at the risk-free rate of interest. The cash flows are discounted continuously at the risk-free rate The option price does not depend on the growth rate of the stock!
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Simulate the stock price t years from now assuming that it grows at the risk-free rate r f. This implies the following relationship: P t = P 0 * exp[(r f -.5*σ 2 )*t + σ*Z*t.5 ] Compute the cash flows from the option at expiration t years from now. Discount the cash flow value back to time 0 by multiplying by e -rt to calculate the current value of the option. Select the current value of the option as the output variable and perform many iterations to quantify the expected value and distribution for the option.
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Variance-Covariance Method ◦ Using an assumed distribution for the asset return (e.g. normally distributed), estimated mean, variances & covariance, compute the associated probability for the VaR Historical Simulation ◦ Use sorted time series data to identify the percentile value associated with the desired VaR Monte Carlo Simulation ◦ Specify probability distributions & correlations for relevant market risk factors and build a simulation model that describes the relationship between the market risk factors and the asset return. After performing iterations, identify the return that produces the desired percentile for the VaR.
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Use options to create other securities ◦ Bull spreads (written and purchased calls) ◦ Collars (stock, written call and purchased put) ◦ PPUP (Principal-Protected, upside potential: bond plus at-the-money call) ◦ Butterfly Options can be replicated by a long or short position in the underlying stock and a long or short position in the risk-free asset (e.g. bond)
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