As usual, the best material at EphBlog is often in the comments. Example from a member of the class of 2020:

I was a WOW attendee last year, and while I was on campus I had the opportunity to listen to a few presentations given by admissions staff that provided us w/ fairly specific statistics about the program.

Because the college itself isn’t all that forthcoming about providing this numbers, I think it might be of (some) use for me to catalog them here. First, total admittance and the sort of people admitted to WOW:

Out of 1200 applicants, Williams admits roughly 200 to WOW. That provides for an admit rate of around 1/6, which is, coincidentally, also the admit rate of the college as a whole.

Those 200 students pick between a WOW session in October and one in September, and they usually do attend. The number I was quoted by admissions staff is that only a few admitted students don’t attend the program at all. (I believe the number was 5-10, but, I can’t recall with any real certainty.)

Of the students that actually attend WOW, which is of course a touch less than the 200 admitted, 70% actually end up applying to the college. So if we’re being generous, we now have 140 WOW attendees who have actually applied to the school. Out of those applicants, 85-90% will be admitted. (I can recall this figure fairly precisely, because, as a WOW attendee desperate to get admitted to the college, it seemed important to remember)

The next piece of information is a touch discontinuous from the first several in form, but, it’s what I was told so it’s what I’ll repeat: out of all WOW attendees, 50 matriculate the succeeding fall.

So, how might we calculate a yield rate out of that number? If we do it out of total attendees 50/200, then we’re left with a yield of 25% — fairly dismal; however, if we grind through the numbers and calculate the actual yield of WOW attendees who apply to the program and then are admitted, we’re left with an imprecise yield rate of 40%

That’s not startlingly different from the college’s overall yield rate. And, while it may be so that attending WOW did increase those students’ chance of attending Williams (perhaps they would have otherwise gone to HYPS) there’s no doubt that at least some in the broader college community would be miffed to learn that the college spends a pretty penny on flying students out only to yield one in four of them.

I have some other anecdotes about the program and fly-ins I could probably share, but, as none of them are really material to what we’re discussing here, I think I’ll end this post before it gets much longer.