"UM is among a distinguished group of 115 institutions including Harvard, MIT and Johns Hopkins in the “highest research,” or R-1 category. This group represents the top 2.5 percent of institutions of higher education.
The Carnegie Classification analyzes Integrated Postsecondary Education Data System, or IPEDS, data from all U.S. post-secondary institutions and evaluates measures of research activity for doctoral universities in making its assessments, which are released every five years."
http://news.olemiss.edu/um-recognized-among-countrys-elite-research-universities/