| Year | Value (SE) |
|---|---|
| 2000 | 0.6193 (0.0285) |
| 2001 | 0.4585 (0.0252) |
| 2002 | 0.9865 (0.0396) |
| 2003 | 0.9118 (0.0407) |
| 2004 | 0.7841 (0.0305) |
| 2005 | 0.8159 (0.0202) |
| 2006 | 0.7876 (0.0249) |
| 2007 | 0.8082 (0.0634) |
| 2008 | 0.9241 (0.0569) |
| 2009 | 0.8793 (0.0331) |
| 2010 | 0.7947 (0.0861) |
| 2011 | 0.8948 (0.0495) |
| 2013 | 0.9339 (0.0887) |
| 2014 | 1.0531 (0.1176) |
| 2015 | 1.0478 (0.1863) |
| 2016 | 0.8542 (0.0491) |
| 2019 | 0.8791 (0.0597) |
| 2022 | 1.1483 (0.3615) |
| 2023 | 0.9314 (0.1741) |
