| Year | Value (SE) |
|---|---|
| 2000 | 0.9670 (0.2261) |
| 2001 | 0.3420 (0.1218) |
| 2002 | 1.0890 (0.3266) |
| 2003 | 0.8430 (0.1342) |
| 2005 | 0.5070 (0.1373) |
| 2007 | 0.7760 (0.1587) |
| 2008 | 1.1650 (0.1844) |
| 2010 | 0.9050 (0.1499) |
| 2012 | 0.8210 (0.1528) |
| 2013 | 1.0750 (0.2548) |
| 2015 | 0.5320 (0.1585) |
| 2019 | 0.4340 (0.1789) |
