You may be right about that.
One could compare scolleges based on distributions of “pre-professional” majors identified in the Common Data Set, section J1. The following majors seem to comprise a reasonable set:
Agriculture 1
NaturalResources 3
Architecture 4
Communications 9
Education 13
Engineering 14
EngineeringTech 15
Parks/Recreation 31
PublicAdministration 44
Health 51
Business/marketing 52
(the numbers are the CIP 2010 category codes for those majors, as shown in the CDS section J)
For 7 Ivies and 6 “public Ivies”, the first column below shows the percentages of graduating seniors in those 11 majors (which I’ve counted from the 2015-16 CDS numbers, except for Harvard for which I used the available 2014-15 CDS). The last column shows the Washington Monthly 2015 National Universities “Bachelor’s to PhD Rank”
52% Cornell (9)
44% UPenn (26)
44% Texas (57)
42% Wisconsin (33)
39% Princeton (3)
34% Michigan (28)
33% Virginia (29)
33% UNC-CH (40)
32% Berkeley (17)
16% Brown (6)
9% Yale (7)
8% Dartmouth (10)
6% Harvard (19)
So I think PurpleTitan is right to point out that pre-professional majors are popular at some Ivies/equivalents.
Pre-professional majors are much more popular at the 6 public Ivies listed above than they are at at least 4 of the actual Ivies; this kind of “intellectual diversity” may partially account for lower per capita PhD production at some public Ivies. However, PhD production is relatively high at Penn, and very high at Cornell and Princeton, even though pre-professional majors seem to be as popular at these 3 Ivies as they are at Public Ivies.
Columbia doesn’t seem to publish a CDS so it’s not listed above.