| Year | Value (SE) |
|---|---|
| 2003 | 0.2048 (0.0234) |
| 2004 | 0.2084 (0.0273) |
| 2005 | 0.2827 (0.0229) |
| 2006 | 0.1351 (0.0161) |
| 2008 | 0.3388 (0.0711) |
| 2009 | 0.2779 (0.0365) |
| 2010 | 0.3852 (0.0747) |
| 2011 | 0.2679 (0.0328) |
| 2013 | 0.5951 (0.0976) |
| 2014 | 0.4939 (0.0917) |
| 2015 | 0.1412 (0.0672) |
| 2019 | 0.4231 (0.0961) |
| 2020 | 1.0634 (0.6428) |
| 2023 | 0.6653 (0.2024) |
