What percentage of STEM PhD applicants have peer-reviewed publications? I am simply looking for a rough estimate on how many PhD applicants typically apply having published a peer-reviewed paper (or papers).

Particularly, I am interested in Computer Science (or STEM fields in general).

Also, it would be interesting to know the same percentage for the admitted students.

These questions can likely only be answered by those on (or previously on) admissions committees, but all responses are welcomed!
I'm in a CS department at a mid-ranked school in the US, and have reviewed applications for Ph.D programs in CS for the last 6 years. I didn't compile detailed numbers, but my sense is that the number of candidates with "actual" publications (as opposed to fluff pubs) is of the order of 5%. I suspect this number is higher for the top-ranked school.