| Year | Value (SE) |
|---|---|
| 2003 | 0.8323 (0.0956) |
| 2004 | 0.7288 (0.0952) |
| 2005 | 0.8100 (0.0657) |
| 2006 | 0.8291 (0.1005) |
| 2008 | 0.9792 (0.2099) |
| 2009 | 0.8965 (0.1140) |
| 2010 | 1.1961 (0.2305) |
| 2011 | 1.0149 (0.1213) |
| 2013 | 1.0743 (0.1750) |
| 2014 | 0.9937 (0.1834) |
| 2015 | 0.6991 (0.3319) |
| 2019 | 0.8634 (0.1952) |
| 2020 | 1.7097 (1.0330) |
| 2023 | 1.2506 (0.3795) |
