| Year | Value (SE) |
|---|---|
| 2003 | 0.8215 (0.1107) |
| 2004 | 0.4366 (0.0803) |
| 2005 | 0.6164 (0.0823) |
| 2006 | 0.7147 (0.1137) |
| 2008 | 0.9126 (0.2538) |
| 2009 | 1.0731 (0.2714) |
| 2010 | 0.7021 (0.1506) |
| 2011 | 0.8393 (0.2236) |
| 2013 | 0.8508 (0.1803) |
| 2014 | 0.7403 (0.1852) |
| 2015 | 0.4391 (0.2262) |
| 2019 | 0.5163 (0.1747) |
| 2020 | 0.5334 (0.3867) |
| 2023 | 1.0480 (0.6464) |
