| Year | Value (SE) |
|---|---|
| 2008 | 0.6291 (0.1255) |
| 2009 | 0.6684 (0.0847) |
| 2011 | 0.5954 (0.0569) |
| 2012 | 0.9666 (0.1669) |
| 2013 | 0.6762 (0.1333) |
| 2014 | 0.6894 (0.1276) |
| 2015 | 1.0732 (0.5452) |
| 2016 | 0.5847 (0.0813) |
| 2018 | 0.5952 (0.1216) |
| 2019 | 0.7220 (0.0865) |
| 2020 | 0.6936 (0.1963) |
| 2021 | 0.9313 (0.6006) |
| 2022 | 1.1793 (0.5518) |
| 2023 | 0.5635 (0.2849) |
