| Year | Value (SE) |
|---|---|
| 2009 | 0.9521 (0.0681) |
| 2010 | 0.8503 (0.2211) |
| 2011 | 0.8283 (0.0268) |
| 2012 | 0.7829 (0.0348) |
| 2013 | 0.7974 (0.0661) |
| 2014 | 0.9599 (0.1174) |
| 2015 | 0.8776 (0.1649) |
| 2016 | 0.8287 (0.0465) |
| 2017 | 0.7676 (0.0729) |
| 2018 | 0.8727 (0.1284) |
| 2019 | 0.7723 (0.1022) |
| 2020 | 0.6595 (0.3319) |
| 2022 | 1.1225 (0.5689) |
| 2023 | 0.6495 (0.1200) |
