Here is the snapshot of yield rates of top schools last year (see the bar graph in the middle):
http://www.thedp.com/article/2017/08/class-of-2021-yield-rate
If the application numbers increase while the applicant numbers stay the same we should see yields drop. But the general trend at top schools is that yields kept roughly the same or even rising a little in recent years. That indicates to me that there is just more demand at the top end of colleges than in the past.