| Year | Value (SE) |
|---|---|
| 2009 | 0.7766 (0.0279) |
| 2010 | 0.7833 (0.0640) |
| 2011 | 0.7159 (0.0105) |
| 2012 | 0.6542 (0.0123) |
| 2013 | 0.7849 (0.0361) |
| 2014 | 0.7176 (0.0363) |
| 2015 | 1.0126 (0.1090) |
| 2016 | 0.8814 (0.0207) |
| 2017 | 0.7331 (0.0244) |
| 2018 | 0.8546 (0.0615) |
| 2019 | 0.6050 (0.0298) |
| 2020 | 0.7481 (0.1901) |
| 2022 | 0.7041 (0.1044) |
| 2023 | 0.9844 (0.0637) |
