A note on methodology: 4-year colleges and universities.

There are two primary goals to our methodology. First, we considered no single category to be more important than any other. Second, the Final rankings needed to reflect excellence across the full breadth of our measures, rather than reward an exceptionally high focus on, say, research. Thus, all three main categories were weighted equally when calculating the final score. In order to ensure that each measurement contributed equally to a school's score within any given category, we standardized each data set so that each had a mean of zero and a standard deviation of one. The data was also adjusted to account for statistical outliers. No school's performance in any single area was allowed to exceed Five standard deviations from the mean of the data set. Thanks to rounding, some schools have the same overall score. We have ranked them according to their pre-rounding results.

To establish the set of colleges included in the rankings, we started with the 1,761 colleges that are listed in the U.S. Department of Education's Integrated Postsecondary Education Data System as having a Carnegie basic classification of research, master's, baccalaureate, and baccalaureate/associate's colleges and are not exclusively graduate schools. We then excluded 143 colleges which reported that at least half of the undergraduate degrees awarded in 2010-11 were not bachelor's degrees, as well as thirteen colleges with fewer than 100 undergraduate students in fall 2011. Next, we decided to exclude the Five federal military academies (Air Force, Army, Coast Guard, Merchant Marine, and Navy) because their unique missions make them difficult to evaluate using our methodology. Our rankings are based in part on the percentage of students receiving Pell Grants and the percentage of students enrolled in the Reserve Officers' Training Corps (ROTC), whereas the service academies provide all students with free tuition (and thus no Pell Grants) and commission graduates as officers in the armed services (and thus not the ROTC program). Our Final set of exclusions was to not rank colleges that had not reported any of the three main measures used in the social mobility section (percent Pell, graduation rate, and net price) in the past three years. This resulted in a final sample of 1,572 colleges and includes public, private nonprofit, and for-profit colleges.

Each of our three categories includes several components. We have determined the community service score by measuring...