United States National Research Council rankings

The United States National Research Council conducts a survey and compiles a report on United States Research-Doctorate Programs approximately every 10 years, although the time elapsed between each new ranking has exceeded 10 years.
Methodology
Data collection for the most recent report began in June 2006; it was released on September 28, 2010. These rankings did not provide exact ranks for any university or doctoral program; rather, a statistical range was given. This was because "the committee felt strongly that assigning to each program a single number and ranking them accordingly would be misleading, since there are significant uncertainties and variability in any ranking process."
Two series of rankings were offered:

The R-rankings were based on regression analysis. According to the NRC, this analysis was "based on an indirect approach to determining what faculty value in a program" and was done by first asking a sample faculty group
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