Not sure this is true anymore.
Even 5 years ago, the percentage had slipped at PEA and other top BSs as colleges changed their admissions priorities.
The last public breakdown I could find showed Exeter at about 19% to Ivies per year (2016-2018). 171 students / 900 (roughly) graduates over 3 years.
To Harvard: 2%. (Surprised how many people still seem to think Exeter is a golden ticket to H).
And I do agree with @lilyesh that at least half are legacies (which is helpful but not a guarantee, obviously) or athletes, but I can’t confirm. Just an anecdotal count of graduates we know.