| Year | Value (SE) |
|---|---|
| 2003 | 0.6914 (0.1161) |
| 2004 | 0.3944 (0.1276) |
| 2005 | 0.9379 (0.5093) |
| 2006 | 1.1936 (0.3141) |
| 2008 | 1.0419 (0.3883) |
| 2009 | 0.4556 (0.1741) |
| 2010 | 0.5030 (0.1570) |
| 2011 | 0.3482 (0.1418) |
| 2013 | 0.5417 (0.1516) |
| 2014 | 0.7638 (0.3015) |
| 2015 | 0.2915 (0.1637) |
| 2019 | 1.9116 (1.4361) |
| 2020 | 0.5126 (0.4129) |
| 2023 | 0.7954 (0.5550) |
