| Year | Value (SE) |
|---|---|
| 2005 | 0.8940 (0.0262) |
| 2006 | 0.9670 (0.0258) |
| 2007 | 1.3700 (0.3796) |
| 2008 | 0.8750 (0.0872) |
| 2009 | 1.0360 (0.0267) |
| 2010 | 0.8510 (0.0546) |
| 2011 | 1.0010 (0.0214) |
| 2012 | 1.0070 (0.0200) |
| 2013 | 0.9560 (0.0433) |
| 2014 | 0.9790 (0.0424) |
| 2016 | 0.9710 (0.0230) |
| 2017 | 0.9540 (0.0220) |
| 2018 | 0.9850 (0.0239) |
| 2019 | 1.0080 (0.0287) |
| 2020 | 1.4160 (0.2026) |
| 2021 | 1.0360 (0.1403) |
| 2022 | 0.7770 (0.0981) |
| 2023 | 1.1020 (0.0887) |
| 2024 | 0.9620 (0.1590) |
