| Year | Value (SE) |
|---|---|
| 2008 | 0.7174 (0.0918) |
| 2009 | 0.6166 (0.0728) |
| 2013 | 0.8795 (0.1662) |
| 2014 | 0.6294 (0.1497) |
| 2015 | 0.7998 (0.2280) |
| 2016 | 0.5429 (0.0937) |
| 2017 | 0.7886 (0.0919) |
| 2018 | 0.6308 (0.1767) |
| 2019 | 0.6093 (0.1478) |
| 2020 | 0.4540 (0.2428) |
| 2021 | 0.9326 (0.9526) |
| 2022 | 0.5270 (0.3044) |
| 2023 | 0.6936 (0.2903) |
