| Year | Value (SE) |
|---|---|
| 2003 | 0.9600 (0.0626) |
| 2004 | 0.8080 (0.0256) |
| 2005 | 0.9030 (0.0267) |
| 2006 | 0.8700 (0.0653) |
| 2008 | 0.7340 (0.0993) |
| 2009 | 0.8620 (0.0604) |
| 2010 | 0.9910 (0.0838) |
| 2011 | 0.9930 (0.0816) |
| 2013 | 0.9440 (0.0747) |
| 2014 | 0.7880 (0.0800) |
| 2015 | 0.7260 (0.2035) |
| 2019 | 0.8600 (0.1402) |
| 2020 | 0.8200 (0.2009) |
| 2023 | 0.6430 (0.0860) |
