| Year | Value (SE) |
|---|---|
| 2007 | 0.9160 (0.0515) |
| 2008 | 0.9920 (0.2337) |
| 2009 | 0.8540 (0.1297) |
| 2010 | 0.9920 (0.1143) |
| 2011 | 0.8560 (0.1314) |
| 2012 | 0.7700 (0.0595) |
| 2013 | 0.6580 (0.0657) |
| 2014 | 0.9640 (0.0949) |
| 2015 | 0.7670 (0.0955) |
| 2016 | 0.8350 (0.0631) |
| 2017 | 0.8060 (0.0775) |
| 2018 | 0.8890 (0.1404) |
| 2019 | 0.9070 (0.1210) |
| 2020 | 0.9910 (0.1708) |
| 2021 | 1.0040 (0.2263) |
| 2022 | 0.9850 (0.2974) |
| 2023 | 0.8890 (0.1637) |
| 2024 | 0.7430 (0.1850) |
