| Year | Value (SE) |
|---|---|
| 2000 | 0.6466 (0.2857) |
| 2001 | 0.5051 (0.0426) |
| 2002 | 0.7409 (0.0696) |
| 2003 | 0.8233 (0.0928) |
| 2004 | 0.6428 (0.1274) |
| 2005 | 0.6721 (0.1229) |
| 2006 | 0.6833 (0.0909) |
| 2007 | 0.8326 (0.0668) |
| 2008 | 0.9959 (0.1628) |
| 2009 | 0.6770 (0.1017) |
| 2010 | 0.7570 (0.1450) |
| 2011 | 0.7719 (0.1717) |
| 2012 | 0.8467 (0.0976) |
| 2013 | 1.0685 (0.2346) |
| 2014 | 0.9205 (0.1511) |
| 2015 | 0.4783 (0.1267) |
| 2016 | 0.5859 (0.0646) |
| 2019 | 0.7757 (0.1360) |
| 2020 | 0.4563 (0.1081) |
| 2021 | 0.2930 (0.2955) |
| 2022 | 0.5287 (0.1551) |
| 2023 | 0.7186 (0.1380) |
