Editing Implied volatility (section)

==Non-constant implied volatility==
In general, options based on the same underlying but with different strike values and expiration times will yield different implied volatilities. This can be viewed as evidence that an underlying's volatility is not constant but instead depends on factors such as price level or time, or it can be viewed as evidence that the underlying's price changes do not follow the distribution that is assumed in the model under consideration (such as Black-Scholes). There exist few known parametrisation of the volatility surface (Schonbusher, SVI, and gSVI) as well as their de-arbitraging methodologies.<ref>{{cite journal |first=Babak |last=Mahdavi Damghani |year=2013|title= De-arbitraging With a Weak Smile: Application to Skew Risk |journal=[[Wilmott (magazine)|Wilmott]] |volume=2013 |issue=1 |pages=40–49 |doi= 10.1002/wilm.10201|s2cid=154646708 }}</ref> See [[stochastic volatility]] and [[volatility smile]] for more information.