| Year | Value (SE) |
|---|---|
| 2003 | 0.7975 (0.1254) |
| 2004 | 0.4373 (0.1413) |
| 2005 | 1.0456 (0.5675) |
| 2006 | 1.2525 (0.3262) |
| 2008 | 0.7810 (0.2863) |
| 2009 | 0.4381 (0.1663) |
| 2010 | 0.4168 (0.1272) |
| 2011 | 0.3407 (0.1370) |
| 2013 | 0.4760 (0.1295) |
| 2014 | 0.6057 (0.2351) |
| 2015 | 0.3027 (0.1610) |
| 2019 | 1.9040 (1.4100) |
| 2020 | 0.2459 (0.1902) |
| 2023 | 0.4089 (0.2814) |
