I've tried "white replacement data" and "white replacement stats" and "white replacement statistics" (without quote marks) with no luck in the last 2 years.

The closest I've found is [1] which is a downvoted comment saying:

> Census data indicate White population has shrunk since 2010

Why is this the first bullet point? Why a focus on White people? Why do you care HN?

The only other place I see stuff like this is when it’s used as an alt-right talking point, or by white-supremacist mass-shooters who write about ‘The Great Replacement’ [1]

So that isn't even arguing against collection of stats. But it's the closest I've been able to find.

Perhaps you are misremembering?

[1] https://news.ycombinator.com/item?id=23735866

Another extremely unsatisfying possibility is that those threads could have been flagged as flame wars and de-indexed. I'm not entirely sure what happened, but I do distinctly remember reading those posts and I'm willing to stand by that.

Fwiw, I couldn't find anything resembling what you're saying in the last 2 years under "great replacement" and similar terms.