| Year | Value (SE) |
|---|---|
| 2000 | 0.8322 (0.0686) |
| 2001 | 0.8610 (0.0086) |
| 2002 | 0.9025 (0.0251) |
| 2003 | 0.8199 (0.0497) |
| 2004 | 0.8281 (0.0406) |
| 2005 | 0.7995 (0.0212) |
| 2006 | 0.7641 (0.0247) |
| 2007 | 0.8826 (0.0373) |
| 2008 | 0.8504 (0.0342) |
| 2009 | 1.0521 (0.0573) |
| 2010 | 1.0690 (0.1312) |
| 2011 | 0.9992 (0.0410) |
| 2012 | 0.8069 (0.0271) |
| 2013 | 1.0423 (0.1065) |
| 2014 | 0.9379 (0.0628) |
| 2015 | 0.9363 (0.1600) |
| 2016 | 0.8084 (0.0322) |
| 2019 | 0.9521 (0.1062) |
| 2020 | 1.0272 (0.2930) |
| 2021 | 0.8837 (0.6538) |
| 2022 | 0.9819 (0.3091) |
| 2023 | 0.8671 (0.0958) |
