| Year | Value (SE) |
|---|---|
| 2008 | 0.9380 (0.0314) |
| 2009 | 1.0340 (0.0226) |
| 2010 | 0.9630 (0.0628) |
| 2011 | 0.9710 (0.0097) |
| 2013 | 0.9190 (0.0519) |
| 2014 | 0.9230 (0.0530) |
| 2015 | 1.2100 (0.2562) |
| 2016 | 1.0090 (0.0438) |
| 2017 | 0.9430 (0.0263) |
| 2018 | 1.0090 (0.0466) |
| 2019 | 0.9370 (0.0376) |
| 2020 | 0.9230 (0.1408) |
| 2021 | 0.9930 (0.1432) |
| 2023 | 1.0780 (0.1213) |
| 2024 | 0.9650 (0.2411) |
