| Year | Value (SE) |
|---|---|
| 2003 | 1.0060 (0.0917) |
| 2004 | 0.7900 (0.2322) |
| 2005 | 0.5130 (0.1247) |
| 2012 | 0.7530 (0.0637) |
| 2013 | 1.0740 (0.1710) |
| 2014 | 0.7780 (0.1942) |
| 2015 | 0.6590 (0.1298) |
| 2016 | 0.7170 (0.0672) |
| 2017 | 0.7590 (0.1469) |
| 2018 | 0.9870 (0.1689) |
| 2019 | 0.7600 (0.1178) |
| 2020 | 0.9150 (0.2610) |
