| Year | Value (SE) |
|---|---|
| 2010 | 0.8070 (0.0223) |
| 2011 | 0.7770 (0.0318) |
| 2012 | 0.8950 (0.0588) |
| 2013 | 0.6390 (0.0307) |
| 2014 | 0.6180 (0.0324) |
| 2015 | 0.6680 (0.0322) |
| 2017 | 0.6820 (0.0394) |
| 2018 | 0.6800 (0.0487) |
| 2019 | 0.7250 (0.0293) |
| 2020 | 0.7070 (0.0312) |
| 2021 | 0.7560 (0.0359) |
| 2022 | 0.7130 (0.0414) |
| 2023 | 0.5970 (0.0424) |
