For the article, “Who Keeps Billions of Taxpayer Dollars Flowing to For-Profit Colleges? These Guys,” ProPublica looked at college student outcome data broken down by accrediting agency to see how accreditors compare to each other.

There are two main types of accreditors: national and regional. The most commonly known accreditors are regional, and they mainly accredit public and private non-profit schools. National accreditors primarily focus on career and vocational schools, which include many for-profit schools. For the analysis, ProPublica focused on some of the largest national accreditation organizations, specifically: the Accrediting Council for Independent Colleges and Schools, the Accrediting Commission of Career Schools and Colleges, the Accrediting Council for Continuing Education and Training, the Council on Occupational Education, and the National Accrediting Commission of Career Arts and Sciences.

For this analysis, ProPublica used accreditation and college outcome data from the Department of Education, including a new federal database called College Scorecard. We used the most recent accreditation stats (from September 2015), and the most recent college outcome data (from 2013). Our analysis only includes schools that are in good standing with their accreditors (we excluded any schools that have actions against them, such as being on probation or having their accreditation terminated, so that we could look at only schools that kept accreditation regardless of their students’ outcomes). Additionally, we limited our analysis to schools that received “institutional” accreditation from the agencies, which typically can be used to establish eligibility for federal aid programs.

Accreditation data is notoriously difficult to analyze. In order to analyze the new College Scorecard data by accreditor, ProPublica had to merge two different databases using unique IPEDS ids as the crosswalk.

The analysis focuses on four key variables: completion rate, default rate, repayment rate and median debt level of graduates. Completion rate at four-year schools is the number of students who graduate within 6 years. The metric only tracks first-time, full-time students and thus excludes any part-time or transfer students, but it remains one of the best indicators of graduation. Default rate represents the percentage of student borrowers who default on their loans within three years of starting repayment. Repayment rate, first released with the new College Scorecard data this past September, indicates the number of former students who took out federal student loans and were able to pay off at least one dollar of the loan principal within three years of leaving school. Median debt level tracks the average amount of federal debt of students who graduate from the institution.

For our analysis, we aggregated the raw numbers from each school and calculated the average broken down by accreditor and length of program (two year or four year programs). We did not calculate the completion rate for two-year programs, since those can be skewed due to a high transfer rate. For our metric, we used a median, in order to avoid skewing from high and low outliers. For our national averages, we used statistics calculated by the Department of Education when available, and in other places, calculated our own metrics based on the College Scorecard database.