| Year | Value (SE) |
|---|---|
| 2003 | 0.5735 (0.1434) |
| 2007 | 0.7266 (0.2519) |
| 2008 | 0.5110 (0.0410) |
| 2009 | 0.8316 (0.0979) |
| 2010 | 0.7215 (0.0996) |
| 2011 | 0.6863 (0.0594) |
| 2012 | 0.7435 (0.0724) |
| 2013 | 0.6849 (0.1544) |
| 2014 | 0.8228 (0.2134) |
| 2015 | 0.3035 (0.0872) |
| 2018 | 0.5693 (0.0522) |
| 2019 | 0.5939 (0.0903) |
| 2020 | 0.8690 (0.4103) |
| 2021 | 0.3963 (0.1625) |
| 2022 | 0.4959 (0.1680) |
| 2023 | 0.4758 (0.1123) |
