| Year | Value (SE) |
|---|---|
| 2000 | 0.5569 (0.2503) |
| 2001 | 0.3897 (0.0331) |
| 2002 | 0.7115 (0.0698) |
| 2003 | 0.6885 (0.0835) |
| 2004 | 0.5464 (0.1088) |
| 2005 | 0.5498 (0.1010) |
| 2006 | 0.5795 (0.0790) |
| 2007 | 0.7714 (0.0687) |
| 2008 | 0.9175 (0.1521) |
| 2009 | 0.7020 (0.1076) |
| 2010 | 0.8224 (0.1686) |
| 2011 | 0.7397 (0.1668) |
| 2012 | 0.6711 (0.0802) |
| 2013 | 1.0148 (0.2287) |
| 2014 | 0.8878 (0.1494) |
| 2015 | 0.5149 (0.1494) |
| 2016 | 0.4891 (0.0561) |
| 2019 | 0.6964 (0.1318) |
| 2020 | 0.5243 (0.1330) |
| 2021 | 0.5393 (0.5993) |
| 2022 | 0.4222 (0.1346) |
| 2023 | 0.6205 (0.1287) |
