| Year | Value (SE) |
|---|---|
| 2002 | 0.5067 (0.0720) |
| 2007 | 0.7907 (0.1046) |
| 2008 | 0.8679 (0.0941) |
| 2009 | 0.7445 (0.0811) |
| 2010 | 0.7879 (0.0907) |
| 2011 | 0.7430 (0.0584) |
| 2012 | 0.7981 (0.0730) |
| 2013 | 0.5686 (0.1031) |
| 2014 | 0.8592 (0.1951) |
| 2015 | 0.4450 (0.1168) |
| 2018 | 0.7060 (0.0635) |
| 2019 | 0.8289 (0.1256) |
| 2020 | 0.5602 (0.2223) |
| 2021 | 0.5295 (0.3345) |
| 2022 | 0.6599 (0.1298) |
| 2023 | 0.5241 (0.1259) |
| 2024 | 0.4856 (0.1725) |
| 2025 | 0.4102 (0.2326) |
