re: Michael Burry calls passive investments/index funds a bubble

I would look at the annual statement and see if they hold any options or futures. I just checked my Vanguard ones and they all do.

ETA: I am no expert. It is just something I have looked at over the years and wondered how all these funds traded the exact same stocks in the exact same percentages and new ETFs and new funds constantly being created. When you read the fine print they use derivatives to bridge the gaps and some ETFs that claim to track are all created in the "lab" so to speak.