| Year | Value (SE) |
|---|---|
| 2008 | 0.9860 (0.0667) |
| 2009 | 0.7950 (0.0345) |
| 2010 | 0.9660 (0.1064) |
| 2011 | 0.9870 (0.0165) |
| 2013 | 0.9850 (0.1365) |
| 2014 | 1.0200 (0.1212) |
| 2015 | 0.6400 (0.2490) |
| 2016 | 0.9460 (0.0671) |
| 2017 | 0.9090 (0.0376) |
| 2018 | 0.9810 (0.0857) |
| 2019 | 1.0860 (0.0763) |
| 2020 | 1.7510 (0.8615) |
| 2021 | 1.1340 (0.4221) |
| 2023 | 0.9990 (0.2448) |
| 2024 | 0.6000 (0.2393) |
