When time decay reverses

Time decay (negative theta) is the norm for long options, yet one of the following long European positions can have positive theta — it gains value purely from the passage of time, all else fixed. Which one, and for the right reason?

Show hints (2)+
  1. Value == decaying time-value ++ the discounting of any locked-in intrinsic value.
  2. For which instrument does a rising discount factor erTe^{-rT} (as T0T\to0) help the holder — a claim to receive the strike, or to pay it?

Answer

Reveal answer →

A deep in-the-money European put — its value is dominated by the discounted strike KerTKe^{-rT}, whose present value rises as T0T\to0

Want the full step-by-step worked solution? It's part of Premium — along with a worked solution for every question in the bank.

Asked at: SIG, DRW

Related questions