| Year | Value (SE) |
|---|---|
| 2003 | 0.8557 (0.1114) |
| 2004 | 0.5403 (0.0992) |
| 2005 | 0.6826 (0.0903) |
| 2006 | 0.8215 (0.1220) |
| 2008 | 1.2433 (0.3174) |
| 2009 | 1.2449 (0.3076) |
| 2010 | 0.7085 (0.1473) |
| 2011 | 0.8452 (0.2210) |
| 2013 | 0.9013 (0.1870) |
| 2014 | 0.9394 (0.2258) |
| 2015 | 0.6048 (0.2830) |
| 2019 | 0.6004 (0.1937) |
| 2020 | 0.6505 (0.4672) |
| 2023 | 1.6299 (1.0003) |
