| Year | Value (SE) |
|---|---|
| 2000 | 0.4532 (0.1114) |
| 2001 | 0.0538 (0.0197) |
| 2002 | 0.5482 (0.1694) |
| 2003 | 0.5288 (0.0908) |
| 2005 | 0.3890 (0.1062) |
| 2007 | 0.6153 (0.1359) |
| 2008 | 0.9543 (0.1741) |
| 2010 | 0.7278 (0.1671) |
| 2012 | 0.5434 (0.1084) |
| 2013 | 0.8230 (0.2159) |
| 2015 | 0.4845 (0.1770) |
| 2019 | 0.6043 (0.2542) |
