| Year | Value (SE) |
|---|---|
| 2008 | 0.7600 (0.0867) |
| 2009 | 0.9530 (0.0355) |
| 2010 | 1.1380 (0.0912) |
| 2011 | 0.9500 (0.0291) |
| 2012 | 0.9260 (0.0276) |
| 2013 | 0.9910 (0.0511) |
| 2014 | 1.0090 (0.0545) |
| 2015 | 0.9880 (0.1334) |
| 2016 | 0.8190 (0.0327) |
| 2017 | 0.7900 (0.0340) |
| 2018 | 0.8090 (0.0334) |
| 2019 | 0.9530 (0.0381) |
| 2020 | 1.2100 (0.1990) |
| 2021 | 0.9800 (0.2523) |
| 2022 | 0.7480 (0.1193) |
| 2023 | 0.8070 (0.0646) |
| 2024 | 0.9640 (0.3055) |
