bmcrhino
While that number may be too high, it's not unreasonable. Using the HBS numbers, there were about 195 people who were admitted who did not matriculate at HBS. If you're applying to HBS, there probably aren't too many reasons you wouldn't go if you were accepted. The primary reason would be you got into Stanford GSB OR received a major scholarship at another top school. So, for 145 of the 195 students to fall into the "Admitted to both" camp is not unreasonable IMO.
And HBS's reported yield is 89%.
Not only is it unreasonable, its mathematically impossible. For a 932 enrollee class to represent an 89% yield suggests there were 115 admittees that chose not to attend. Versus your 195 figure, you're only off by 70%.
I'd be very surprised if over 50% of the HBS rejectors ended up at GSB (much less the 75% you suggested on a mathematically impossible base of 195 rejectors). I'd speculate a good portion of them decide not to go to b-school all together or end up going to another school.
It might be a no-brainer if HBS/GSB are your dream schools, but for the supposed "shoe in" candidates HBS is par for the course and not nearly the marked upward deviation from their current mean trajectory.