| Year | Value (SE) |
|---|---|
| 2000 | 0.9295 (0.2988) |
| 2001 | 0.6070 (0.0718) |
| 2002 | 1.0360 (0.1004) |
| 2003 | 0.8950 (0.0771) |
| 2004 | 0.9188 (0.1314) |
| 2005 | 0.6952 (0.1074) |
| 2006 | 0.7311 (0.0706) |
| 2007 | 0.6674 (0.0540) |
| 2008 | 0.8716 (0.1870) |
| 2009 | 0.5076 (0.0826) |
| 2010 | 1.1043 (0.2910) |
| 2011 | 0.3561 (0.1139) |
| 2012 | 0.6558 (0.0730) |
| 2013 | 0.6797 (0.1174) |
| 2014 | 0.7495 (0.1660) |
| 2015 | 0.4174 (0.1858) |
| 2016 | 0.6424 (0.1526) |
| 2018 | 0.7179 (0.1702) |
| 2019 | 0.8960 (0.1944) |
| 2020 | 0.7592 (0.2358) |
| 2021 | 0.3873 (0.2983) |
| 2022 | 0.7314 (0.4692) |
| 2023 | 0.7874 (0.2485) |
