| Year | Value (SE) |
|---|---|
| 2000 | 0.6553 (0.1332) |
| 2001 | 0.5382 (0.0164) |
| 2002 | 0.8193 (0.0405) |
| 2003 | 0.9312 (0.0804) |
| 2004 | 0.8225 (0.0775) |
| 2005 | 0.9037 (0.0698) |
| 2006 | 0.8752 (0.0728) |
| 2007 | 0.8987 (0.0589) |
| 2008 | 0.9020 (0.0810) |
| 2009 | 0.8104 (0.0592) |
| 2010 | 0.9394 (0.1413) |
| 2011 | 0.8165 (0.0858) |
| 2012 | 0.9707 (0.0729) |
| 2013 | 1.0526 (0.1307) |
| 2014 | 0.7699 (0.0738) |
| 2015 | 0.8613 (0.2081) |
| 2016 | 0.7954 (0.0574) |
| 2019 | 0.8655 (0.1282) |
| 2020 | 1.0014 (0.2386) |
| 2021 | 0.5919 (0.6403) |
| 2022 | 0.7153 (0.1973) |
| 2023 | 0.8258 (0.1487) |
