| Year | Value (SE) |
|---|---|
| 2003 | 0.8970 (0.2202) |
| 2007 | 1.3060 (0.3667) |
| 2008 | 0.8000 (0.0559) |
| 2009 | 0.8510 (0.0822) |
| 2010 | 0.7620 (0.0502) |
| 2011 | 0.8670 (0.0952) |
| 2012 | 1.0080 (0.0856) |
| 2013 | 0.9840 (0.1987) |
| 2014 | 1.4060 (0.3411) |
| 2015 | 0.4150 (0.0944) |
| 2018 | 0.7840 (0.0554) |
| 2019 | 0.8320 (0.1047) |
| 2020 | 1.2760 (0.4654) |
| 2021 | 0.6580 (0.1336) |
| 2022 | 0.8210 (0.1547) |
| 2023 | 0.8150 (0.1468) |
