Vega-Weighted Least Squares and Bid-Ask Penalty Splines in SVI Optimizers
Unweighted implied volatility OLS gives a $0.05 nickel wing put with a 6-vol bid-ask spread the same pull as a 0.08-vol-wide ATM straddle, distorting ATM pricing.
Điểm chính: Inverse implied-volatility spread squared w_i = 1 / (IV_ask - IV_bid)^2 = Vega_i^2 / DollarSpread_i^2 is the statistically optimal Gauss-Markov weight across strikes.
