| Year | Value (SE) |
|---|---|
| 2002 | 0.5067 (0.0720) |
| 2007 | 0.7907 (0.1046) |
| 2008 | 0.6686 (0.0502) |
| 2009 | 0.6008 (0.0579) |
| 2010 | 0.7972 (0.0463) |
| 2011 | 0.7430 (0.0584) |
| 2012 | 0.7363 (0.0664) |
| 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 | 0.5764 (0.2936) |
| 2021 | 0.5295 (0.3345) |
| 2022 | 0.6599 (0.1298) |
| 2023 | 0.5241 (0.1259) |
| 2024 | 0.4856 (0.1725) |
