| Year | Value (SE) |
|---|---|
| 2000 | 0.7350 (0.0945) |
| 2001 | 0.1540 (0.0330) |
| 2002 | 0.8730 (0.0982) |
| 2003 | 0.9260 (0.1183) |
| 2004 | 1.0000 (0.3815) |
| 2005 | 0.7490 (0.1726) |
| 2006 | 1.1600 (0.1589) |
| 2007 | 0.4410 (0.0779) |
| 2008 | 1.3220 (0.1599) |
| 2009 | 0.9500 (0.0976) |
| 2010 | 0.8940 (0.1044) |
| 2011 | 1.4420 (0.2812) |
| 2013 | 1.1420 (0.2199) |
| 2014 | 1.2440 (0.2720) |
| 2015 | 0.5650 (0.1073) |
| 2016 | 0.7370 (0.0875) |
| 2019 | 1.4310 (0.2636) |
| 2022 | 0.2900 (0.2259) |
| 2023 | 1.0670 (0.4368) |
