| Year | Value (SE) |
|---|---|
| 2008 | 0.9150 (0.0500) |
| 2009 | 1.0220 (0.0268) |
| 2011 | 0.9650 (0.0134) |
| 2012 | 0.9530 (0.0251) |
| 2013 | 0.9820 (0.0500) |
| 2014 | 0.9550 (0.0442) |
| 2015 | 0.9230 (0.1000) |
| 2016 | 1.0090 (0.0437) |
| 2018 | 1.0010 (0.0342) |
| 2019 | 0.9830 (0.0209) |
| 2020 | 1.0050 (0.0763) |
| 2021 | 0.7530 (0.1095) |
| 2022 | 0.7320 (0.0777) |
| 2023 | 1.0290 (0.1118) |
