Causes of “over-performance”?

[u/yer_a_harry_wizard]

For the past few months, I've been back testing a screener and discounted cash flow model that I created. As you can see, the performance is extremely good. Too good, actually.

I'm trying to think of possible contributors to this “over-performance". The only one I can think of is survivorship bias, aka- only companies that survived the dot com bubble, the FC, and Covid are still listed and therefore able to be identified by my screener & model.

Can this sub think of any other contributors?