Lesson 8 of 8 · All lessons in this module
  1. Present value and discount (zero-coupon) bondsVideo lesson
  2. Coupon bonds and perpetual bonds
  3. Level-payment instruments: mortgages and amortizing loansVideo lesson
  4. Valuing shares with dividend discount models
  5. Implied returns on bonds
  6. Required return, implied growth and the P/E ratio
  7. Cash flow additivity, no arbitrage and forward rates
  8. No-arbitrage pricing of FX forwards and options

Lesson 8 of 8 · 15 min

No-arbitrage pricing of FX forwards and options

The same no-arbitrage logic sets forward exchange rates (two riskless deposits must end equal) and option values (a riskless share-plus-option portfolio must earn the risk-free rate).

In short

  • Depositing in the base currency must equal converting at spot, depositing in the price currency and converting back at the forward rate.
  • With continuous rates and price/base quotes: Fp/b=Sp/be(rp−rb)TF_{p/b} = S_{p/b}e^{(r_p - r_b)T}.
  • The higher-rate currency trades at a forward discount; the lower-rate currency at a forward premium.
  • One-period binomial model: combine shares and an option so the portfolio is worth the same whether the price goes up or down.
  • Call: buy h shares and sell one call. Put: buy h shares and buy one put. Discount the riskless end value at r to get today's option price.
  • The number of shares per option is the hedge ratio.

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