| Year | Value (SE) |
|---|---|
| 2000 | 0.6255 (0.0528) |
| 2001 | 0.2351 (0.0324) |
| 2002 | 0.5703 (0.0375) |
| 2003 | 0.6944 (0.0582) |
| 2004 | 0.4664 (0.0661) |
| 2005 | 0.7526 (0.0670) |
| 2006 | 0.6187 (0.0436) |
| 2007 | 0.9166 (0.1377) |
| 2008 | 0.7926 (0.0707) |
| 2009 | 0.7723 (0.0470) |
| 2010 | 0.7472 (0.0911) |
| 2011 | 0.7098 (0.0760) |
| 2013 | 0.6864 (0.0937) |
| 2014 | 0.6571 (0.0996) |
| 2015 | 0.6761 (0.1325) |
| 2016 | 0.7708 (0.0693) |
| 2019 | 0.5670 (0.0751) |
| 2022 | 2.2183 (1.6743) |
| 2023 | 0.8490 (0.3364) |
