| Year | Value (SE) |
|---|---|
| 2003 | 0.2940 (0.0114) |
| 2004 | 0.2940 (0.0231) |
| 2005 | 0.1500 (0.0110) |
| 2008 | 0.8160 (0.1690) |
| 2009 | 0.2590 (0.0523) |
| 2010 | 0.5320 (0.0309) |
| 2011 | 0.5090 (0.0397) |
| 2012 | 0.2820 (0.0162) |
| 2013 | 0.4530 (0.0411) |
| 2014 | 0.4140 (0.0439) |
| 2015 | 0.3040 (0.0439) |
| 2016 | 0.3470 (0.0243) |
| 2017 | 0.4020 (0.0295) |
| 2018 | 0.5110 (0.0544) |
| 2021 | 0.1770 (0.0549) |
| 2022 | 0.2990 (0.0625) |
| 2024 | 0.1810 (0.1210) |
