| Year | Value (SE) |
|---|---|
| 2003 | 0.8890 (0.0383) |
| 2007 | 0.7520 (0.1411) |
| 2008 | 0.9880 (0.0672) |
| 2009 | 1.0210 (0.0420) |
| 2010 | 0.9680 (0.0243) |
| 2011 | 0.8350 (0.0298) |
| 2012 | 0.9490 (0.0268) |
| 2013 | 0.7550 (0.0689) |
| 2014 | 0.8920 (0.0752) |
| 2015 | 0.7560 (0.1264) |
| 2018 | 0.8730 (0.0440) |
| 2019 | 0.9350 (0.0729) |
| 2020 | 2.1200 (1.2017) |
| 2021 | 0.4320 (0.1537) |
| 2022 | 0.8520 (0.1072) |
| 2023 | 1.0160 (0.1528) |
