Among the top private universities, Brown, Dartmouth, Princeton, and Cornell have the highest percentage of undergraduates. The rest are more grad-focused. Of HYPSM, Princeton puts the most emphasis on undergraduates. Somehow, maybe that philosophy is reflected in their annual #1 undergrad ranking by USNews. (or maybe it has little to do with it, given the ranks of Dartmouth, Cornell and Brown…)
That said, that’s just one part of the overall “academic fit” variable. Some kids might want more grad students around. (certainly there are pros to go along with the cons). Maybe it doesn’t make that big of a deal – even the schools with lower percentages of undergrads assign enough resources to them to make it a great experience. Certainly undergrads at UChicago aren’t lacking attention or opportunities.
As for the tiers, i had been thinking of them in terms of the whole university – undergrad, grad/pro, and PhD. I would add Johns Hopkins to the Northwestern level and put Duke back on it too. Looking at overall program rankings, Duke is not better than Northwestern, Johns Hopkins or Cornell… and it is not as undergrad-focused as Brown or Dartmouth.
Stanford now does have a bigger international rep than Princeton or Yale, mostly based on its grad programs/research and CS pipeline. But for undergrad quality and focus, I think Yale and Princeton are at least as good.