| Year | Value (SE) |
|---|---|
| 2002 | 1.0770 (0.0638) |
| 2003 | 0.8820 (0.0459) |
| 2004 | 0.8020 (0.0513) |
| 2006 | 0.8870 (0.0181) |
| 2008 | 0.8580 (0.0539) |
| 2009 | 0.9520 (0.0377) |
| 2010 | 1.5280 (0.2525) |
| 2011 | 0.9670 (0.0447) |
| 2013 | 1.0060 (0.1010) |
| 2014 | 1.0730 (0.1017) |
| 2016 | 0.7800 (0.0498) |
| 2019 | 0.9010 (0.0501) |
