The index value typically reflects trading activity of portfolio managers hedging tail risk with options, to protect portfolios from a large, sudden decline in the market"
In 2021 the peak in this index was early relative to the S&P 500 peak - occurring between the implosion of Nasdaq small caps and the implosion of the Nasdaq mega caps.
In October 2018, the index peaked ahead of a -20% drawdown in the fourth quarter with the low in late December.