| Year | Value (SE) |
|---|---|
| 2007 | 0.7790 (0.1017) |
| 2009 | 1.0325 (0.0993) |
| 2010 | 0.9114 (0.1272) |
| 2011 | 0.9182 (0.0471) |
| 2012 | 0.6767 (0.0291) |
| 2013 | 0.9787 (0.0855) |
| 2014 | 0.9090 (0.0562) |
| 2015 | 1.4294 (0.5060) |
| 2016 | 0.7681 (0.0417) |
| 2018 | 0.7934 (0.1067) |
| 2019 | 0.8348 (0.0918) |
| 2020 | 0.5559 (0.1954) |
| 2021 | 1.0450 (1.0912) |
| 2022 | 1.0015 (0.6564) |
| 2023 | 1.0076 (0.2467) |
