| Year | Value (SE) |
|---|---|
| 2009 | 0.9220 (0.0570) |
| 2010 | 0.9580 (0.0576) |
| 2011 | 1.0110 (0.0294) |
| 2012 | 0.9700 (0.0189) |
| 2013 | 1.0620 (0.0630) |
| 2014 | 0.8880 (0.0428) |
| 2015 | 0.9490 (0.0778) |
| 2016 | 1.0310 (0.0223) |
| 2017 | 0.9930 (0.0216) |
| 2018 | 1.0180 (0.0208) |
| 2019 | 1.0220 (0.0196) |
| 2020 | 1.0720 (0.0925) |
| 2021 | 0.8400 (0.1509) |
| 2022 | 1.0100 (0.1513) |
| 2023 | 1.0470 (0.0572) |
| 2024 | 0.8720 (0.1023) |
