| Year | Value (SE) |
|---|---|
| 2008 | 0.7045 (0.1406) |
| 2009 | 0.4662 (0.0721) |
| 2013 | 0.5673 (0.1439) |
| 2014 | 0.3714 (0.1104) |
| 2015 | 0.4807 (0.1543) |
| 2016 | 0.5130 (0.1514) |
| 2017 | 0.7452 (0.1031) |
| 2018 | 0.5973 (0.1901) |
| 2019 | 0.4484 (0.1263) |
| 2020 | 0.6288 (0.3578) |
| 2021 | 0.6024 (0.6266) |
| 2022 | 1.0007 (0.7114) |
| 2023 | 0.7484 (0.3419) |
