| Year | Value (SE) |
|---|---|
| 2000 | 0.8860 (0.1533) |
| 2001 | 0.8490 (0.0502) |
| 2002 | 0.8360 (0.0440) |
| 2003 | 1.0250 (0.0628) |
| 2004 | 0.9190 (0.1198) |
| 2005 | 0.8010 (0.1032) |
| 2006 | 0.8710 (0.0755) |
| 2007 | 0.9620 (0.0365) |
| 2008 | 1.1190 (0.1192) |
| 2009 | 0.7120 (0.0654) |
| 2010 | 0.9960 (0.1029) |
| 2011 | 0.8510 (0.1056) |
| 2012 | 0.8130 (0.0547) |
| 2013 | 0.8710 (0.1066) |
| 2014 | 0.8790 (0.1063) |
| 2015 | 0.6000 (0.0925) |
| 2016 | 0.7240 (0.0702) |
| 2019 | 0.8160 (0.1207) |
| 2020 | 0.8800 (0.1490) |
| 2021 | 1.0500 (0.3540) |
| 2022 | 0.5410 (0.2604) |
| 2023 | 0.8360 (0.1358) |
