| Year | Value (SE) |
|---|---|
| 2009 | 0.6904 (0.0372) |
| 2010 | 0.5987 (0.0975) |
| 2011 | 0.6675 (0.0187) |
| 2012 | 0.6398 (0.0294) |
| 2013 | 0.5515 (0.0661) |
| 2014 | 0.7375 (0.0578) |
| 2015 | 0.8487 (0.2083) |
| 2016 | 0.5977 (0.0315) |
| 2018 | 0.7571 (0.0478) |
| 2019 | 0.7268 (0.0260) |
| 2022 | 0.6910 (0.2490) |
| 2023 | 0.7696 (0.0982) |
| 2024 | 0.3664 (0.1200) |
