| Year | Value (SE) |
|---|---|
| 2008 | 0.8440 (0.0897) |
| 2009 | 0.8564 (0.0786) |
| 2010 | 0.7543 (0.1647) |
| 2011 | 0.8934 (0.0500) |
| 2013 | 0.5974 (0.1133) |
| 2014 | 0.8271 (0.1658) |
| 2015 | 0.8445 (0.4039) |
| 2016 | 0.5932 (0.0724) |
| 2017 | 0.7518 (0.0772) |
| 2018 | 0.6947 (0.1523) |
| 2019 | 1.1524 (0.2994) |
| 2020 | 0.3738 (0.1983) |
| 2021 | 0.4855 (0.1979) |
| 2023 | 0.7922 (0.2876) |
| 2024 | 1.2853 (0.8002) |
