Course episode eight, Wilmott chapter six. Price an option that
expires in months on a stock that moves continuously. Hold the
option and sell delta shares against it; over the next instant the
slope terms cancel exactly and what is left is deterministic, the
option's time decay plus the curvature term from Ito's lemma. A
riskless portfolio must earn the risk-free rate, and setting those
equal is the Black-Scholes equation, stated in words. What fell out:
the stock's expected return never appears, only its volatility, the
continuous version of the binomial tree's lesson. From equation to
price: the payoff at expiry anchors it, and for a plain call the
answer is the Black-Scholes formula, read off the bell curve. One
rule of thumb to carry: an at-the-money short-dated call is worth
about four tenths of the stock price times volatility times the
square root of time, so a three-month call on a hundred-dollar stock
at forty percent volatility is about eight dollars. What the price
means for a desk that hedges, and where the model bends. Vocabulary:
hedge portfolio, delta, riskless over an instant, the risk-free
rate, the Black-Scholes equation, boundary condition, the
Black-Scholes formula. Ends with a prompt to take to your own AI
model.
For educational purposes only; not financial, investment, tax, or
legal advice. Nothing here is a recommendation to buy or sell any
instrument. Past performance is not indicative of future results.
Nothing in this podcast is financial advice. All figures discussed are historical and for educational purposes only. Do your own research and consult a licensed professional before making investment decisions.