| Year | Value (SE) |
|---|---|
| 2000 | 0.5927 (0.0273) |
| 2001 | 0.3609 (0.0200) |
| 2002 | 0.8790 (0.0355) |
| 2003 | 0.8471 (0.0379) |
| 2004 | 0.7386 (0.0288) |
| 2005 | 0.7874 (0.0196) |
| 2006 | 0.7223 (0.0232) |
| 2007 | 0.8115 (0.0636) |
| 2008 | 0.9241 (0.0569) |
| 2009 | 0.8740 (0.0329) |
| 2010 | 0.7947 (0.0861) |
| 2011 | 0.8796 (0.0487) |
| 2013 | 0.9002 (0.0854) |
| 2014 | 1.0657 (0.1189) |
| 2015 | 0.9011 (0.1603) |
| 2016 | 0.8354 (0.0480) |
| 2019 | 0.8483 (0.0577) |
| 2022 | 1.0714 (0.3373) |
| 2023 | 0.8784 (0.1643) |
