| 2011 | 11.80% | 14.63% |
| 2012 | 11.80% | 14.73% |
| 2013 | 11.80% | 15.26% |
| 2014 | 11.80% | 14.21% |
| 2015 | 11.80% | 14.28% |
| 2016 | 11.80% | 14.81% |
| 2017 | 11.80% | 14.48% |
| 2018 | 11.80% | 15.43% |
| 2019 | 11.80% | 14.87% |