| Year | Value (SE) |
|---|---|
| 2009 | 1.0920 (0.1174) |
| 2010 | 0.9890 (0.1120) |
| 2011 | 0.8560 (0.0340) |
| 2012 | 0.9730 (0.0316) |
| 2013 | 0.9570 (0.0818) |
| 2014 | 1.0350 (0.1025) |
| 2015 | 0.9300 (0.1160) |
| 2016 | 0.8680 (0.0312) |
| 2017 | 0.8780 (0.0272) |
| 2018 | 0.8940 (0.0307) |
| 2019 | 0.9090 (0.0267) |
| 2020 | 1.0570 (0.1987) |
| 2021 | 1.0940 (0.4039) |
| 2022 | 1.4750 (0.4141) |
| 2023 | 1.0170 (0.0980) |
| 2024 | 0.9110 (0.2965) |
