| Year | Value (SE) |
|---|---|
| 2003 | 0.8080 (0.0993) |
| 2004 | 0.7300 (0.2108) |
| 2005 | 1.3740 (0.7360) |
| 2006 | 1.4530 (0.3409) |
| 2008 | 0.8380 (0.2628) |
| 2009 | 0.3660 (0.1335) |
| 2010 | 0.7100 (0.1776) |
| 2011 | 0.4120 (0.1616) |
| 2013 | 0.6010 (0.1388) |
| 2014 | 0.8130 (0.2889) |
| 2015 | 0.4820 (0.1771) |
| 2019 | 3.1840 (2.3020) |
| 2020 | 0.7880 (0.4265) |
| 2023 | 0.4880 (0.3081) |
