| Year | Value (SE) |
|---|---|
| 2009 | 0.9830 (0.0351) |
| 2010 | 1.0320 (0.0851) |
| 2011 | 0.9120 (0.0130) |
| 2012 | 0.8630 (0.0158) |
| 2013 | 0.9400 (0.0436) |
| 2014 | 1.0460 (0.0525) |
| 2015 | 1.3610 (0.1463) |
| 2016 | 0.9750 (0.0227) |
| 2017 | 0.9280 (0.0306) |
| 2018 | 1.1410 (0.0829) |
| 2019 | 0.8910 (0.0438) |
| 2020 | 0.7950 (0.2021) |
| 2022 | 0.6930 (0.1029) |
| 2023 | 1.0540 (0.0683) |
