| Year | Value (SE) |
|---|---|
| 2000 | 0.8512 (0.0663) |
| 2001 | 0.7885 (0.0156) |
| 2002 | 0.9268 (0.0237) |
| 2003 | 0.7588 (0.0400) |
| 2004 | 0.8454 (0.0309) |
| 2005 | 0.8050 (0.0253) |
| 2006 | 0.8072 (0.0261) |
| 2007 | 0.9845 (0.0602) |
| 2008 | 0.8855 (0.0624) |
| 2009 | 1.0946 (0.0711) |
| 2010 | 0.9025 (0.1267) |
| 2011 | 0.8346 (0.0809) |
| 2012 | 0.7585 (0.0398) |
| 2013 | 0.9359 (0.0628) |
| 2014 | 0.9686 (0.0839) |
| 2015 | 1.0204 (0.3152) |
| 2016 | 0.8985 (0.0778) |
| 2018 | 0.8480 (0.0657) |
| 2019 | 0.8977 (0.0812) |
| 2020 | 0.7797 (0.1673) |
| 2021 | 1.0083 (0.7654) |
| 2022 | 1.0117 (0.2425) |
| 2023 | 0.8769 (0.1365) |
