| Year | Value (SE) |
|---|---|
| 2003 | 0.9450 (0.0486) |
| 2004 | 0.7950 (0.0742) |
| 2005 | 0.6900 (0.0543) |
| 2008 | 2.1430 (0.4957) |
| 2009 | 0.9820 (0.2318) |
| 2010 | 1.0150 (0.0764) |
| 2011 | 1.5540 (0.1370) |
| 2012 | 0.7920 (0.0612) |
| 2013 | 1.1090 (0.1380) |
| 2014 | 0.8880 (0.1243) |
| 2015 | 0.7940 (0.1341) |
| 2016 | 0.8300 (0.0707) |
| 2017 | 0.7440 (0.1100) |
| 2018 | 0.7880 (0.1591) |
| 2021 | 1.1230 (0.4330) |
| 2022 | 1.6160 (0.5011) |
| 2024 | 0.8930 (0.8432) |
