| Year | Value (SE) |
|---|---|
| 2001 | 0.2593 (0.0595) |
| 2006 | 0.8562 (0.0358) |
| 2007 | 0.7708 (0.0616) |
| 2008 | 0.6733 (0.0402) |
| 2009 | 0.8045 (0.0569) |
| 2010 | 0.8335 (0.0354) |
| 2011 | 0.7520 (0.0356) |
| 2012 | 0.8275 (0.0478) |
| 2013 | 0.7885 (0.1098) |
| 2014 | 0.8049 (0.1331) |
| 2015 | 1.1949 (0.5927) |
| 2016 | 0.8039 (0.1478) |
| 2018 | 0.6397 (0.0790) |
| 2020 | 0.6157 (0.1862) |
| 2021 | 0.4891 (0.2022) |
| 2022 | 0.4072 (0.0963) |
| 2023 | 0.4224 (0.1120) |
| 2024 | 0.4044 (0.1761) |
