| Year | Value (SE) |
|---|---|
| 2005 | 0.8073 (0.2329) |
| 2006 | 0.8809 (0.0476) |
| 2007 | 1.1494 (0.6509) |
| 2008 | 0.6974 (0.1192) |
| 2009 | 0.9459 (0.0437) |
| 2010 | 1.1701 (0.1844) |
| 2011 | 0.8969 (0.0309) |
| 2012 | 0.8670 (0.0298) |
| 2013 | 0.9187 (0.0748) |
| 2014 | 0.9761 (0.0917) |
| 2016 | 0.9176 (0.0380) |
| 2017 | 0.8710 (0.0360) |
| 2018 | 0.9180 (0.0454) |
| 2019 | 0.9122 (0.0400) |
| 2020 | 0.7264 (0.1735) |
| 2021 | 1.3022 (0.4356) |
| 2022 | 0.8881 (0.2157) |
| 2023 | 0.8893 (0.1231) |
| 2024 | 1.1765 (0.5317) |
