| Year | Value (SE) |
|---|---|
| 2001 | 0.2151 (0.0295) |
| 2002 | 0.4504 (0.0441) |
| 2003 | 0.4560 (0.0255) |
| 2004 | 0.2080 (0.0170) |
| 2005 | 0.3230 (0.0476) |
| 2007 | 0.2650 (0.0413) |
| 2008 | 0.3720 (0.0374) |
| 2009 | 0.2770 (0.0386) |
| 2010 | 0.3410 (0.0403) |
| 2011 | 0.5188 (0.0827) |
| 2012 | 0.2474 (0.0511) |
| 2013 | 0.2346 (0.0432) |
| 2014 | 0.2596 (0.0390) |
| 2015 | 0.7666 (0.7641) |
| 2016 | 0.2488 (0.0566) |
| 2017 | 0.2213 (0.0545) |
| 2018 | 0.5257 (0.1204) |
| 2020 | 0.3926 (0.1230) |
| 2021 | 0.9817 (0.9716) |
| 2022 | 0.4301 (0.0750) |
| 2023 | 0.5539 (0.1269) |
