| Year | Value (SE) |
|---|---|
| 2000 | 0.8340 (0.0440) |
| 2002 | 0.8110 (0.0113) |
| 2003 | 0.9810 (0.0278) |
| 2004 | 0.7780 (0.0303) |
| 2005 | 0.9680 (0.0262) |
| 2006 | 0.8620 (0.0147) |
| 2007 | 0.9130 (0.0127) |
| 2008 | 0.9100 (0.0356) |
| 2009 | 0.7980 (0.0267) |
| 2010 | 0.9100 (0.0531) |
| 2011 | 0.8030 (0.0204) |
| 2012 | 1.0620 (0.0286) |
| 2013 | 0.8540 (0.0368) |
| 2014 | 0.9350 (0.0369) |
| 2015 | 0.7070 (0.0691) |
| 2016 | 0.9330 (0.0312) |
| 2017 | 0.7760 (0.0414) |
| 2020 | 0.6560 (0.1413) |
| 2021 | 0.7810 (0.3002) |
| 2022 | 0.6000 (0.1927) |
| 2023 | 0.7440 (0.0733) |
