| 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 |
| 0.24 | 0.31 | 0.36 | 0.40 | 0.42 | 0.34 | 0.45 | 0.50 | 0.51 |
| 0.23 | 0.36 | 0.37 | 0.41 | 0.45 | 0.48 | 0.52 | 0.57 | 0.62 |
| 0.19 | 0.28 | 0.40 | 0.41 | 0.42 | 0.39 | 0.50 | 0.54 | 0.55 |
| 0.11 | 0.06 | 0.21 | 0.18 | 0.21 | 0.28 | 0.36 | 0.38 | 0.41 |