| Year | Value (SE) |
|---|---|
| 2010 | 0.7080 (0.0163) |
| 2011 | 0.6670 (0.0165) |
| 2012 | 0.6380 (0.0246) |
| 2013 | 0.6660 (0.0177) |
| 2014 | 0.5890 (0.0190) |
| 2016 | 0.6650 (0.0119) |
| 2017 | 0.6170 (0.0177) |
| 2018 | 0.7060 (0.0321) |
| 2019 | 0.5980 (0.0209) |
| 2020 | 0.6370 (0.0183) |
| 2021 | 0.6380 (0.0207) |
| 2022 | 0.5620 (0.0205) |
