| Year | Value (SE) |
|---|---|
| 2008 | 0.9130 (0.0527) |
| 2009 | 0.9710 (0.0237) |
| 2010 | 0.8360 (0.0648) |
| 2011 | 0.9130 (0.0128) |
| 2012 | 0.9520 (0.0129) |
| 2013 | 1.0010 (0.0405) |
| 2014 | 0.9730 (0.0195) |
| 2015 | 0.9030 (0.0910) |
| 2016 | 1.0290 (0.0311) |
| 2017 | 0.9380 (0.0323) |
| 2018 | 0.9880 (0.0508) |
| 2019 | 0.9670 (0.0667) |
| 2020 | 0.8550 (0.1076) |
| 2021 | 1.7010 (1.1442) |
| 2022 | 0.6950 (0.0843) |
