| Year | Value (SE) |
|---|---|
| 2002 | 0.5142 (0.1015) |
| 2003 | 0.6572 (0.1161) |
| 2004 | 0.5646 (0.3995) |
| 2006 | 0.7076 (0.0627) |
| 2008 | 1.0190 (0.1437) |
| 2009 | 0.8949 (0.1202) |
| 2010 | 0.7203 (0.1633) |
| 2011 | 1.0351 (0.1741) |
| 2013 | 0.7325 (0.1964) |
| 2014 | 0.7273 (0.1768) |
| 2016 | 0.5007 (0.0750) |
| 2019 | 0.8097 (0.1743) |
