| Year | Value (SE) |
|---|---|
| 2008 | 0.7757 (0.0340) |
| 2009 | 0.7023 (0.0229) |
| 2013 | 0.4748 (0.0289) |
| 2014 | 0.5701 (0.0277) |
| 2015 | 0.4718 (0.0919) |
| 2016 | 0.7407 (0.0525) |
| 2017 | 0.7089 (0.0315) |
| 2018 | 0.6585 (0.0294) |
| 2019 | 0.2084 (0.0325) |
| 2020 | 0.4869 (0.0656) |
| 2021 | 0.5630 (0.1700) |
| 2022 | 0.6397 (0.1701) |
| 2023 | 0.7080 (0.0673) |
