| Year | Value (SE) |
|---|---|
| 2002 | 0.4774 (0.0933) |
| 2003 | 0.7452 (0.1301) |
| 2004 | 0.7040 (0.4981) |
| 2006 | 0.7977 (0.0702) |
| 2008 | 1.1877 (0.1650) |
| 2009 | 0.9400 (0.1248) |
| 2010 | 0.4714 (0.1050) |
| 2011 | 1.0704 (0.1783) |
| 2013 | 0.7282 (0.1927) |
| 2014 | 0.6778 (0.1625) |
| 2016 | 0.6420 (0.0925) |
| 2019 | 0.8986 (0.1913) |
