1y x 2y ATM Swaption Straddle Rich Relative to 1y x 5y

The ratio of implied vols of the 1y x 2y and 1y x 5y ATM straddles just reached historical highs. It slightly retraced already but is still 2.34 standard deviations away from its historical average. (As for any option, the value of a swaption increases with vol, so a high implied vol on the 1y x 2y option relative to another swaption indicates relative richness.)