Looking at the Common Data Set. It seems like not many high schools report class rank. Even schools like Harvard and Stanford, only about 30 + percent report class rank. U Michigan does not have class rank on CDS. That being said, when a college publishes that the percentages of admitted freshmen is from the top 10 % of their graduating class etc, I would think that would only be on the ones that reported and not that of the whole incoming class as that would be inaccurate since 70 % or so are not reporting class rank. Am I missing something here?
No, except the percentage probably varies by college. The last figure I saw was that slightly over half of US high schools do not report a cardinal/ordinal rank, so some colleges may get a higher percentage of applications from schools that don’t rank, and others lower.
That said, even without a specific rank, an AO can guess fairly closely. The school profile will often list GPA by decile, so an AO can compare where an individual GPA falls on the continuum. Additionally, if multiple applicants from a HS apply to a college, an AO can sort in GPA order.