| Year | Value (SE) |
|---|---|
| 2008 | 0.7860 (0.0978) |
| 2009 | 0.8983 (0.0415) |
| 2011 | 0.9196 (0.0252) |
| 2012 | 0.9177 (0.0435) |
| 2013 | 0.9201 (0.1148) |
| 2014 | 0.9178 (0.0825) |
| 2015 | 1.3956 (0.3782) |
| 2016 | 0.7709 (0.0478) |
| 2018 | 1.0581 (0.0719) |
| 2019 | 0.9407 (0.0360) |
| 2020 | 0.9799 (0.2196) |
| 2021 | 1.7899 (0.9966) |
| 2022 | 0.9772 (0.2792) |
| 2023 | 1.3192 (0.3853) |
