Why a capped put can match an uncapped call
Question
Take a European call and a European put with the same expiry, both struck at the forward price of the stock. They have the same value, even though the call's payoff has no upper limit while the put's payoff can never exceed the strike. How can that be?
Short answer
Put-call parity forces equality, and the distribution is skewed. Call minus put pays , a forward struck at , which is worth zero, so the two prices match. The call's large payoffs come from a long but thin right tail, while the put's payoffs, though capped at , occur on a fat block of downside outcomes; under the lognormal law the expected excesses above and below balance exactly.
Adapted from Joshi, Denson & Downes, Quant Job Interview Questions and Answers, Q2.17, p.18; question and answer rewritten by SelfMadeQuant.com.
See the hint and the full worked solution in the question bank (free account).
Open the worked solutionLessons behind this question
- No-Arbitrage Bounds and Put-Call Parity
- Option Mechanics: Calls, Puts, Moneyness, Intrinsic Value, and Exchange vs. OTC Markets
- Option Trading Strategies: Spreads, Combinations, and Payoff Engineering
Start with a free lesson: Options is part of a free topic. Create a free account, no card needed, to read it in full with worked solutions.
Read it free