| Year | Value (SE) |
|---|---|
| 2000 | 0.5240 (0.1215) |
| 2006 | 0.8770 (0.0985) |
| 2008 | 0.9070 (0.0486) |
| 2009 | 0.9330 (0.0622) |
| 2010 | 0.8270 (0.0451) |
| 2011 | 0.8310 (0.0371) |
| 2012 | 0.9440 (0.1307) |
| 2013 | 0.7930 (0.0792) |
| 2014 | 0.7400 (0.0714) |
| 2016 | 0.4040 (0.0620) |
| 2017 | 0.7980 (0.0898) |
| 2018 | 0.7280 (0.0505) |
| 2019 | 0.5740 (0.0468) |
| 2020 | 0.5070 (0.0655) |
| 2021 | 0.3550 (0.0471) |
| 2022 | 0.2790 (0.0463) |
| 2023 | 0.3150 (0.0476) |
| 2024 | 0.2950 (0.0536) |
