| Year | Value (SE) |
|---|---|
| 2003 | 0.6399 (0.0140) |
| 2007 | 0.3885 (0.0407) |
| 2008 | 0.6817 (0.0182) |
| 2009 | 0.8299 (0.0179) |
| 2010 | 0.7445 (0.0416) |
| 2011 | 0.8677 (0.0129) |
| 2012 | 0.8195 (0.0132) |
| 2013 | 0.8128 (0.0556) |
| 2014 | 0.7814 (0.0404) |
| 2015 | 0.5639 (0.0466) |
| 2018 | 0.7668 (0.0278) |
| 2019 | 0.5947 (0.0284) |
| 2020 | 0.5361 (0.0756) |
| 2021 | 0.5952 (0.1497) |
| 2022 | 0.5934 (0.0496) |
| 2023 | 0.5888 (0.0362) |
