| Year | Value (SE) |
|---|---|
| 2008 | 0.7286 (0.1172) |
| 2009 | 0.7474 (0.0587) |
| 2011 | 0.6824 (0.0364) |
| 2012 | 0.7847 (0.0739) |
| 2013 | 0.7766 (0.1214) |
| 2014 | 0.7856 (0.1040) |
| 2015 | 0.8569 (0.2661) |
| 2016 | 0.8333 (0.0918) |
| 2018 | 0.7523 (0.1387) |
| 2019 | 0.7027 (0.0551) |
| 2020 | 0.6497 (0.1674) |
| 2021 | 0.9594 (0.5664) |
| 2022 | 0.5639 (0.1943) |
| 2023 | 1.0448 (0.5016) |
