| Year | Value (SE) |
|---|---|
| 2002 | 0.7789 (0.2463) |
| 2004 | 0.9184 (0.9464) |
| 2005 | 0.8081 (0.7859) |
| 2007 | 1.4685 (0.4879) |
| 2008 | 0.8923 (0.2582) |
| 2009 | 1.4937 (0.5883) |
| 2010 | 0.6599 (0.1322) |
| 2011 | 0.6956 (0.0741) |
| 2012 | 0.7681 (0.0609) |
| 2013 | 0.6365 (0.0836) |
| 2014 | 0.6795 (0.0788) |
| 2015 | 0.5103 (0.2506) |
