| Year | Value (SE) |
|---|---|
| 2000 | 0.6682 (0.0129) |
| 2002 | 0.7585 (0.0136) |
| 2003 | 0.6413 (0.0112) |
| 2004 | 0.7802 (0.0058) |
| 2005 | 0.7679 (0.0044) |
| 2006 | 0.6936 (0.0073) |
| 2007 | 0.7605 (0.0098) |
| 2008 | 0.6604 (0.0150) |
| 2009 | 0.6888 (0.0128) |
| 2010 | 0.8358 (0.0233) |
| 2011 | 0.6608 (0.0083) |
| 2012 | 0.6398 (0.0091) |
| 2013 | 0.7732 (0.0218) |
| 2014 | 0.7940 (0.0154) |
| 2015 | 0.7905 (0.0421) |
| 2016 | 0.6712 (0.0116) |
| 2017 | 0.4637 (0.0127) |
| 2020 | 0.7335 (0.0717) |
| 2021 | 0.6980 (0.1598) |
| 2022 | 0.6461 (0.1109) |
| 2023 | 0.7871 (0.0430) |
