: The passage of time exerts a deterministic downward pressure on the extrinsic value embedded within options contracts, a phenomenon known as time decay or Theta. This effect accelerates as the option approaches its expiration epoch, particularly for at-the-money instruments. Traders selling options actively seek to profit from this predictable decline in option value.
Valuation
: The theoretical value of an option is constantly being reduced by the time decay factor, independent of the underlying asset’s price trajectory. Sophisticated pricing models explicitly incorporate this rate of change into their calculations for every time step. Understanding this dynamic is key to correctly assessing the fair value of short-dated instruments.
Return
: For option sellers, time decay represents a positive source of expected return, effectively a premium collected for bearing volatility risk over a defined period. Conversely, long option holders experience this decay as a cost that must be overcome by favorable underlying asset movement or increased implied volatility. Realized return calculations must isolate the impact of this time-based erosion.
