| Year | Value (SE) |
|---|---|
| 2008 | 0.7806 (0.0875) |
| 2009 | 0.7810 (0.0742) |
| 2010 | 0.6271 (0.1520) |
| 2011 | 0.8562 (0.0486) |
| 2013 | 0.5408 (0.1071) |
| 2014 | 0.7787 (0.1618) |
| 2015 | 0.6540 (0.3437) |
| 2016 | 0.5662 (0.0739) |
| 2017 | 0.6444 (0.0684) |
| 2018 | 0.6876 (0.1533) |
| 2019 | 1.0745 (0.2850) |
| 2020 | 0.6042 (0.3333) |
| 2021 | 0.5467 (0.2357) |
| 2023 | 0.8532 (0.3228) |
| 2024 | 0.7442 (0.4994) |
