| Year | Value (SE) |
|---|---|
| 2006 | 1.0260 (0.1376) |
| 2008 | 0.8000 (0.0909) |
| 2009 | 0.8550 (0.0657) |
| 2010 | 0.9240 (0.0530) |
| 2011 | 0.8810 (0.0471) |
| 2012 | 0.8010 (0.0639) |
| 2015 | 0.3460 (0.1584) |
| 2016 | 0.4860 (0.2394) |
| 2019 | 0.9030 (0.1889) |
| 2020 | 1.2210 (0.3903) |
| 2021 | 1.0230 (0.5293) |
| 2022 | 0.6050 (0.0957) |
| 2023 | 0.6660 (0.3158) |
