Time decay, also known as theta, is the phenomenon where an option’s extrinsic value diminishes as its expiration date approaches. This erosion of value occurs because the probability of the underlying asset reaching the strike price decreases over time. The rate of time decay accelerates significantly during the final weeks before expiration, particularly for options that are at-the-money.
Impact
The impact of time decay is a direct reduction in the option’s premium, affecting both option buyers and sellers. Option buyers face a continuous loss of value, requiring the underlying asset price to move favorably just to break even. Conversely, option sellers benefit from time decay, as they profit from the reduction in the option’s value over time.
Implication
The strategic implication for traders is the necessity of managing theta risk, especially when holding long option positions. Traders must account for the cost of time decay in their profit calculations and adjust their strategies accordingly. Options strategies like calendar spreads are specifically designed to exploit the difference in time decay between options with different expiration dates.
