| Year | Value (SE) |
|---|---|
| 2008 | 0.5756 (0.1154) |
| 2009 | 0.6831 (0.0863) |
| 2011 | 0.5746 (0.0551) |
| 2012 | 0.9212 (0.1597) |
| 2013 | 0.6640 (0.1326) |
| 2014 | 0.6583 (0.1232) |
| 2015 | 0.9906 (0.5048) |
| 2016 | 0.5900 (0.0816) |
| 2018 | 0.5958 (0.1223) |
| 2019 | 0.7098 (0.0851) |
| 2020 | 0.6971 (0.1972) |
| 2021 | 0.7013 (0.4523) |
| 2022 | 0.8633 (0.4033) |
| 2023 | 0.5799 (0.2933) |
