| Year | Value (SE) |
|---|---|
| 2002 | 0.4643 (0.0926) |
| 2003 | 0.6388 (0.1135) |
| 2004 | 0.4873 (0.3448) |
| 2006 | 0.6913 (0.0615) |
| 2008 | 0.9783 (0.1393) |
| 2009 | 0.9065 (0.1221) |
| 2010 | 0.5928 (0.1368) |
| 2011 | 1.0299 (0.1740) |
| 2013 | 0.7582 (0.2047) |
| 2014 | 0.6938 (0.1696) |
| 2016 | 0.5047 (0.0762) |
| 2019 | 0.7991 (0.1729) |
