Implied Variance (Implied Volatility)

That state of the art method in the market today for estimating the volatility is the impliedvariance estimate. Implied variance can generally be regarded as the market’s opinion about the future variance of the stock. Originally proposed by Latane and Rendleman (1976), the idea behind the estimation of the implied variance is to equate the Black-Scholes model price to the current market price and solve iteratively for the remaining unknown variance. No closed-form solution is available to compute the implied variance, so a numerical search procedure such as the Newton-Raphson search or linear least-squares regression must be used. Issues abound concerning the use of implied variance; the first of them is the weighting issue. If the implied variance inherent in the market price for each outstanding option on a stock (underlying asset) were calculated, there would be as many estimates of the stock’s implied variance as there are options. Disregarding the possibility of market mispricings for the moment, a number of other factors may also be able to help explain the observed discrepancies.