Subject: Re: NDX 100 Momentum Strategy - Code Repository
Ray asked: I have always wondered if GTR1 has the same issue.

I can 100% assure you that the constituent list in GTR1 is accurate back to its conception in 1985. There are few projects I've put more time into than building these point-in-time change lists. And as an FYI: This is also true every single time there is the slightest change in the list every single day.

Backtests that do not maintain constituent lists that are accurate have significant survivorship bias and are useless.