<p>In my 'Why Penn' essay, I said that Penn's student pop. was 16,000. I checked, and it was about 21,000. I forget where, but I read that the student pop. was 16,000 years ago, and I forgot to confirm. Do you that's a deal-breaker? I'm paranoid. :X</p>
<p>I wouldn’t worry about it. If the rest of your essay is good, it shouldn’t be a problem. I think they’re more concerned about who you are and how you would contribute to and take advantage of what Penn has to offer, instead of your command of some random statistics. As long as you didn’t write about how much you’re looking forward to Winter Carnival and spending 4 years in Hanover ;), I think you’re fine.</p>
<p>And by the way, there are about 10,000 undergrads at Penn. The 21,000 number includes graduate and professional students (which may be what you intended to convey).</p>