Frequently Asked Questions

Where did the data come from?
You can learn more about the data sources here.
Why do some of the ranges of rankings on the site differ from those from the NRC?
There are two reasons. First, the NRC's ranking algorithm contains elements of randomness, and we cannot replicate the random numbers used by the NRC in all cases. Second, in some cases the NRC combines multiple programs into one, while we keep them separate. Because our data set has more programs, the resulting rankings are different.
Why are some of the data several years old?
Most of the data sources we use take several years to compile and release their data. As of fall 2010, we are using the most recent data sets available from the NRC and IPEDS. The 2008 Survey of Graduate Students and Postdoctorates in Sciences and Engineering recently became available, and we plan to update from the 2007 survey in early 2011. We also plan to update the Survey of Earned Doctorates data to the 2008 data set at the same time.
Why are there no rankings for programs in my field?
We are only ranking programs in the fields ranked by the National Research Council in their 2010 study.
Why is my program not listed?
There are several possible reasons that a program might not be listed:
  1. We do not have data for all fields (some data are not available for all fields). Your program might be in one of the fields that is not ranked.
  2. Your program may be too small. Programs that produced fewer than 3 PhDs between 2005 and 2009 are not ranked.
  3. Your program may have been grouped together with another program. For some institutions and fields we only have data by field rather than by program. For example, in some cases an applied mathematics program and a pure mathematics program would be grouped together and listed as a mathematics program. This type of aggregation can happen when we have Survey of Earned Doctorates data (which is by field) but no National Research Council data (which is by program).
Why don't you include universities outside the United States?
We would love to include information about universities in other countries. The main obstacle is the availability of data. If you know of a data set that we could use, please let us know about it.
Why is some information missing?
There are two main reasons for missing values:
  1. Survey nonresponse: Many of the data sets we are using are generated from surveys of institutions or doctoral students. When questions in the surveys are unanswered, we end up with missing data.
  2. Confidentiality measures: Some data sets (e.g., the Survey of Earned Doctorates) have values suppressed to protect the confidentiality of survey responders. No values from the SED are reported unless they come from at least 5 survey responses. When reporting sets of percentages that add up to 100, additional suppression is done to prevent one from deducing a suppressed value by subtracting the sum of the remaining values from 100.
How was this project funded?
You can learn more about our funding here.
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