RV = realized vol (annualized log-return stdev × √252) ·
RV-z = current 20d RV vs 1y mean ·
IV = implied vol (ATM ~30d/90d) ·
IV/RV > 1 = options expensive vs realized ·
Skew = 25Δ put IV − 25Δ call IV (positive = put protection bid) ·
Term = 90d − 30d IV (negative = backwardation = stress)