| Year | Value (SE) |
|---|---|
| 2008 | 0.9660 (0.0435) |
| 2009 | 0.9490 (0.0317) |
| 2013 | 0.9630 (0.0599) |
| 2014 | 0.8560 (0.0431) |
| 2015 | 0.8610 (0.1527) |
| 2016 | 0.9810 (0.0779) |
| 2017 | 0.9340 (0.0422) |
| 2018 | 0.9980 (0.0478) |
| 2019 | 1.0620 (0.0829) |
| 2020 | 1.0500 (0.2437) |
| 2021 | 0.9170 (0.2768) |
| 2022 | 0.8960 (0.2382) |
| 2023 | 1.0600 (0.0829) |
