| Year | Value (SE) |
|---|---|
| 2000 | 0.9640 (0.0725) |
| 2001 | 0.8300 (0.0158) |
| 2002 | 0.9860 (0.0216) |
| 2003 | 0.8320 (0.0418) |
| 2004 | 0.8600 (0.0312) |
| 2005 | 0.8610 (0.0266) |
| 2006 | 0.9090 (0.0258) |
| 2007 | 1.0440 (0.0600) |
| 2008 | 0.9390 (0.0624) |
| 2009 | 1.1510 (0.0712) |
| 2010 | 0.9470 (0.1268) |
| 2011 | 0.8430 (0.0753) |
| 2012 | 0.8830 (0.0410) |
| 2013 | 0.9540 (0.0610) |
| 2014 | 0.9010 (0.0748) |
| 2015 | 1.0520 (0.3078) |
| 2016 | 0.9330 (0.0778) |
| 2018 | 0.8000 (0.0599) |
| 2019 | 0.9570 (0.0790) |
| 2020 | 0.8890 (0.1853) |
| 2021 | 0.9250 (0.7007) |
| 2022 | 1.3490 (0.3164) |
| 2023 | 0.8320 (0.1272) |
