I just returned from a Labor Day weekend getaway and saw your interesting post. MIT and Harvard are the big feeder schools for your program followed by Princeton and Yale. Not surprising.
Brandeis is a surprise with five (too large to be a fluke).
I am also surprised by U Delaware (although they have an outstanding chem program due to affiliation with DuPont, as I recall).
Also surprised by U Maryland Baltimore County, since U Maryland College Park is the system flagship. My brother is in the immunology PhD program at U Maryland Baltimore (not Baltimore County). I know there is collaboration among JHU and the local U Maryland campuses and that universities in the Baltimore area have strong programs in biomedical science.
A little surprised by Michigan State. I wonder if grad programs build connections (partnerships?) with certain undergrad schools, perhaps due to common research interests and collaboration among faculty.
Thanks for the very interesting information. I think prospective students would find it useful.
By the way, it is a lot of work. I try to do it as easily as possible by downloading files of bachelors degree data from IPEDS Peer Analysis System, sorting by IPEDS ID number, and merging with the data from Survey of Earned Doctorates by ID number using SAS software. Still a lot of work.
Glad someone appreciates it.