| Year | Value (SE) |
|---|---|
| 2008 | 0.7463 (0.1482) |
| 2009 | 0.4959 (0.0760) |
| 2013 | 0.5934 (0.1481) |
| 2014 | 0.3286 (0.0975) |
| 2015 | 0.4676 (0.1411) |
| 2016 | 0.6218 (0.1779) |
| 2017 | 0.7919 (0.1060) |
| 2018 | 0.8239 (0.2602) |
| 2019 | 0.5468 (0.1499) |
| 2020 | 0.6925 (0.3600) |
| 2021 | 0.1899 (0.1890) |
| 2022 | 0.9172 (0.6061) |
| 2023 | 1.0196 (0.4593) |
