| Year | Value (SE) |
|---|---|
| 2001 | 0.1395 (0.0763) |
| 2006 | 0.7911 (0.0522) |
| 2007 | 0.8001 (0.0955) |
| 2008 | 0.8857 (0.1216) |
| 2009 | 0.6994 (0.0850) |
| 2010 | 0.6712 (0.1107) |
| 2011 | 0.6859 (0.0751) |
| 2012 | 0.7757 (0.0768) |
| 2013 | 0.6821 (0.1565) |
| 2014 | 0.5691 (0.1655) |
| 2015 | 0.6034 (0.4128) |
| 2016 | 0.6415 (0.2105) |
| 2018 | 0.6532 (0.1055) |
| 2020 | 0.5123 (0.1831) |
| 2021 | 0.3737 (0.1653) |
| 2022 | 0.5029 (0.1754) |
| 2023 | 0.3895 (0.1248) |
| 2024 | 0.3769 (0.1781) |
