A529612,
You short put is short theta, therefore you do not want time value to increase (it will increase the premium). Time value decreases with time but can increase as a result of higher implied volatility. You are short implied volatility (you donât want it to rise). Conversely, if implied drops, your time value will decrease at a greater rate than normal time decay. However, a fall in implied is usually accompanied by a fall in the underlying.
Time value is more a reflection of implied volatility rather than time to expiry. Time value on options on different underlying but with identical strikes, times to expiry, and underlying prices can vary because of different implied volatilities; the higher the implied, the higher the premium.
(Deep in-the-money calls sometimes trade at a discount/below intrinsic value (underlying â strike) effectively having no time value/zero implied volatility.)
Vega tells us how much an option will change for a 1% change in implied. For long puts (and calls) this is positive, meaning higher implied will increase the value of the premium; it is negative for short puts (and calls), ie lower implied will decrease the premium.
Generally, the greater a put is out-of-the-money, the higher the implied, the greater the vega in percentage terms but lower in point terms.
For calls, the further out-of-the-money, the lower the implied, the lower the vega in point terms but higher in percentage terms. See the attached Word.doc for an illustration (you may have to scroll up the page). The inconsistency in the lowest strikes for calls possibly reflects the tendency to a reducing extrinsic value (I may be out of my depth here. And itâs very late here in England).
The ranking is based on Last Trade implied so the strikes, deltas are not perfectly sequential, and skews may be distorted to a degree.
Good trading.
Grant.