| Year | Value (SE) |
|---|---|
| 2002 | 1.0030 (0.1877) |
| 2003 | 1.0180 (0.1713) |
| 2004 | 1.4280 (1.0054) |
| 2006 | 0.9800 (0.0840) |
| 2008 | 1.3270 (0.1672) |
| 2009 | 1.1020 (0.1413) |
| 2010 | 0.8730 (0.1351) |
| 2011 | 1.1880 (0.1920) |
| 2013 | 1.1100 (0.2751) |
| 2014 | 1.0880 (0.2429) |
| 2016 | 0.7430 (0.1003) |
| 2019 | 0.9560 (0.1987) |
