| Year | Value (SE) |
|---|---|
| 2008 | 0.9820 (0.1843) |
| 2009 | 0.7560 (0.1062) |
| 2013 | 0.6450 (0.1473) |
| 2014 | 0.5900 (0.1602) |
| 2015 | 0.5650 (0.1250) |
| 2016 | 0.4100 (0.0760) |
| 2017 | 0.9450 (0.1167) |
| 2018 | 0.9470 (0.2889) |
| 2019 | 0.7360 (0.1894) |
| 2020 | 0.7090 (0.1638) |
| 2021 | 0.6460 (0.1670) |
| 2022 | 1.8990 (1.0674) |
| 2023 | 1.0790 (0.4708) |
