| Year | Value (SE) |
|---|---|
| 2008 | 0.7963 (0.1272) |
| 2009 | 0.7313 (0.0580) |
| 2011 | 0.7071 (0.0373) |
| 2012 | 0.8234 (0.0764) |
| 2013 | 0.7908 (0.1210) |
| 2014 | 0.8226 (0.1066) |
| 2015 | 0.9284 (0.2858) |
| 2016 | 0.8259 (0.0917) |
| 2018 | 0.7515 (0.1378) |
| 2019 | 0.7149 (0.0559) |
| 2020 | 0.6464 (0.1668) |
| 2021 | 1.2741 (0.7523) |
| 2022 | 0.7703 (0.2661) |
| 2023 | 1.0153 (0.4873) |
