The stats from last year are on the same blog, blog post dated: 13 Jan 2012.
Here is a excerpt:
"Now, please pay attention - this is a new level of transparency that I hope is helpful, but I need you to understand that I am talking about what happened in Round 1 vs. telling you exactly what will happen in Round 2 (which we obviously DON'T KNOW now).
The pattern of interview invitation volume in Round 1 was:
Week 1 (first wave of invitations): 750 invitations sent
Week 2 (second wave): 80 invitations sent
Week 3 (third/final wave): 25 invitations sent
Round 2 won't be identical, but I think it will be directionally similar. Please hear me when I say that the timing of the interview invitation is NOT a signal of the strength of a candidate. The only thing that it maps to is the ability of our Admissions Board to move through their (large) reading allocations."