| Year | Value (SE) |
|---|---|
| 2005 | 0.3910 (0.3019) |
| 2006 | 1.1170 (0.1838) |
| 2007 | 0.9730 (0.3072) |
| 2008 | 1.4840 (0.2505) |
| 2009 | 1.0160 (0.1052) |
| 2010 | 1.1000 (0.1345) |
| 2011 | 1.2410 (0.1268) |
| 2012 | 1.1260 (0.1190) |
| 2013 | 0.8630 (0.0992) |
| 2014 | 1.0960 (0.1420) |
| 2016 | 0.9950 (0.0767) |
| 2017 | 1.0380 (0.0906) |
| 2018 | 0.8830 (0.1238) |
| 2019 | 1.2820 (0.1616) |
| 2020 | 0.8780 (0.2199) |
| 2021 | 0.7750 (0.1765) |
| 2022 | 1.6430 (0.7430) |
| 2023 | 1.0170 (0.2117) |
| 2024 | 0.6070 (0.2528) |
