Retention rates
The following are Northwestern's retention rates to the second, third and fourth year.
| 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | |
| 2nd | 79% | 76% | 77% | 79% | 78% | 82% | 82% | 77% | 75% | 76% |
| 3rd | 70% | 69% | 72% | 73% | 71% | 72% | 73% | 66% | 66% | |
| 4th | 66% | 65% | 65% | 69% | 66% | 65% | 69% | 65% |
