| Year | Value (SE) |
|---|---|
| 2000 | 0.8961 (0.2899) |
| 2001 | 0.5038 (0.0598) |
| 2002 | 1.0214 (0.1001) |
| 2003 | 0.7446 (0.0665) |
| 2004 | 0.7902 (0.1133) |
| 2005 | 0.5985 (0.0927) |
| 2006 | 0.6646 (0.0648) |
| 2007 | 0.6968 (0.0598) |
| 2008 | 0.8184 (0.1774) |
| 2009 | 0.5843 (0.0962) |
| 2010 | 1.0458 (0.2819) |
| 2011 | 0.3002 (0.0977) |
| 2012 | 0.5790 (0.0660) |
| 2013 | 0.6484 (0.1139) |
| 2014 | 0.6753 (0.1523) |
| 2015 | 0.4391 (0.2030) |
| 2016 | 0.5993 (0.1445) |
| 2018 | 0.5744 (0.1378) |
| 2019 | 0.8575 (0.1907) |
| 2020 | 0.6750 (0.2238) |
| 2021 | 0.3583 (0.3074) |
| 2022 | 0.9866 (0.6442) |
| 2023 | 0.6551 (0.2159) |
