| Year | Value (SE) |
|---|---|
| 2009 | 0.8810 (0.0101) |
| 2010 | 0.9130 (0.0360) |
| 2011 | 0.7040 (0.0085) |
| 2012 | 0.6300 (0.0086) |
| 2013 | 0.5900 (0.0197) |
| 2014 | 0.7420 (0.0122) |
| 2015 | 0.7000 (0.0342) |
| 2016 | 0.7530 (0.0125) |
| 2017 | 0.9090 (0.0185) |
| 2018 | 0.8180 (0.0185) |
| 2019 | 0.8410 (0.0083) |
| 2020 | 0.8270 (0.0170) |
| 2021 | 0.7760 (0.0099) |
| 2022 | 0.7890 (0.0168) |
