| Year | Value (SE) |
|---|---|
| 2008 | 0.9500 (0.1551) |
| 2009 | 0.9840 (0.0926) |
| 2010 | 0.9420 (0.1251) |
| 2011 | 0.7310 (0.0554) |
| 2012 | 0.9910 (0.0609) |
| 2013 | 0.7640 (0.0638) |
| 2014 | 0.8250 (0.0573) |
| 2015 | 1.1760 (0.2370) |
| 2016 | 0.8180 (0.0867) |
| 2017 | 0.9650 (0.0996) |
| 2018 | 1.0890 (0.1894) |
| 2019 | 0.9090 (0.1992) |
| 2020 | 0.7880 (0.1457) |
| 2021 | 1.1110 (0.4195) |
| 2022 | 0.8020 (0.2982) |
