Vega is a measurement of the amount an option contract’s price changes in response to a 1% change in the implied volatility of the underlying asset.
Understanding vega in options trading
Vega is one of the standard Greek risk measures used in options pricing alongside delta, gamma, and theta. It applies to both call and put options. When the implied volatility of an underlying asset increases, the price of the option generally increases. This happens because higher volatility indicates a greater statistical likelihood that the underlying asset will experience a large price swing before the expiration date.
The value of vega changes over the life of an option contract. Vega is highest for options that are exactly at-the-money. As the strike price of the option moves further in-the-money or out-of-the-money, the vega value decreases. Time to expiration also dictates the vega value. Options with a long time until expiration have higher vega values than short-term options, since there is more time for volatility fluctuations to affect the price of the underlying asset.
Elephants trading options use vega to calculate their exposure to changing market conditions. A long option position has a positive vega, meaning the position gains value as implied volatility rises. A short option position has a negative vega, meaning the seller of the option loses money if implied volatility increases. Traders monitor vega to ensure their portfolios are not overly exposed to sudden spikes or drops in market volatility.
Example
Suppose an Elephant buys a call option on Marula Fruit International stock. The option currently trades at a premium of 2.50 and has a vega of 0.15. The implied volatility of the stock is currently 20%. Weather forecasts predict an unexpected drought across the savanna, causing traders to anticipate erratic price movements for the company. This causes the implied volatility to jump from 20% to 22%, representing an increase of 2 percentage points. Because the vega is 0.15, the option premium increases by 0.30, which is calculated by multiplying the 2% change by the 0.15 vega value. The new premium for the call option is 2.80, assuming the underlying stock price and the time to expiration remain constant.