| Year | Value (SE) |
|---|---|
| 2008 | 0.9230 (0.0823) |
| 2009 | 1.0510 (0.0535) |
| 2010 | 1.0350 (0.1413) |
| 2011 | 1.0130 (0.0235) |
| 2012 | 0.9720 (0.0280) |
| 2013 | 1.0560 (0.0822) |
| 2014 | 0.9710 (0.0411) |
| 2015 | 1.1780 (0.2132) |
| 2016 | 0.8450 (0.0309) |
| 2017 | 0.9980 (0.0528) |
| 2018 | 0.9850 (0.0579) |
| 2019 | 1.0780 (0.0654) |
| 2020 | 0.9540 (0.3406) |
| 2021 | 2.4650 (1.7801) |
| 2022 | 1.1110 (0.2943) |
| 2023 | 0.8260 (0.1520) |
