This is really incredible, catching all the prior crashes going back that far.

One question that I have is: This seems to indicate long periods of being out of NDX after a crash. For example, after the 2010 Flash Crash there is no BULL signal till the 2020 COVID Recovery ? That would be 10 years out of the market during the long bull run of the 2010s ?

If the system provides a signal for re-entry after each crash, it would be so much more useful.