| Year | Value (SE) |
|---|---|
| 2001 | 0.4520 (0.0501) |
| 2006 | 1.0050 (0.0382) |
| 2007 | 0.9310 (0.0594) |
| 2008 | 0.8210 (0.0536) |
| 2009 | 0.8300 (0.0460) |
| 2010 | 0.7910 (0.1046) |
| 2011 | 0.8430 (0.0370) |
| 2012 | 0.9600 (0.0528) |
| 2013 | 0.9490 (0.1123) |
| 2014 | 0.8540 (0.1308) |
| 2015 | 1.6060 (0.7596) |
| 2016 | 1.2580 (0.2149) |
| 2018 | 0.9700 (0.0980) |
| 2020 | 0.5300 (0.1474) |
| 2021 | 0.6590 (0.2416) |
| 2022 | 0.6370 (0.1359) |
| 2023 | 0.5670 (0.1404) |
| 2024 | 0.6330 (0.2336) |
