| Year | Value (SE) |
|---|---|
| 2009 | 0.8201 (0.1206) |
| 2010 | 0.7902 (0.0968) |
| 2011 | 0.7627 (0.0583) |
| 2012 | 0.7872 (0.0565) |
| 2013 | 0.6661 (0.0733) |
| 2014 | 0.9874 (0.1362) |
| 2015 | 0.8268 (0.1120) |
| 2016 | 0.7352 (0.0400) |
| 2017 | 0.6980 (0.0459) |
| 2018 | 0.7581 (0.0602) |
| 2019 | 0.8299 (0.0629) |
| 2020 | 0.9027 (0.2052) |
| 2021 | 1.2712 (0.5122) |
| 2022 | 0.8540 (0.3124) |
| 2023 | 0.7048 (0.1476) |
| 2024 | 0.9611 (0.3495) |
