| Year | Value (SE) |
|---|---|
| 2001 | 0.5460 (0.0456) |
| 2006 | 0.9290 (0.0163) |
| 2007 | 0.8770 (0.0421) |
| 2008 | 0.9620 (0.0455) |
| 2009 | 0.9610 (0.0263) |
| 2010 | 0.9660 (0.0632) |
| 2011 | 0.8930 (0.0164) |
| 2012 | 0.9450 (0.0291) |
| 2013 | 0.9410 (0.0689) |
| 2014 | 1.0070 (0.0628) |
| 2015 | 0.7440 (0.1114) |
| 2016 | 0.8950 (0.0597) |
| 2018 | 0.7750 (0.0555) |
| 2020 | 0.9220 (0.1098) |
| 2021 | 0.9140 (0.1751) |
| 2022 | 0.7530 (0.0781) |
| 2023 | 0.6730 (0.0641) |
| 2024 | 1.2100 (0.2774) |
