| Year | Value (SE) |
|---|---|
| 2000 | 0.7080 (0.0523) |
| 2001 | 0.6320 (0.0407) |
| 2002 | 0.8620 (0.0612) |
| 2003 | 0.9000 (0.0564) |
| 2005 | 0.8620 (0.0290) |
| 2007 | 0.8970 (0.0740) |
| 2008 | 1.1190 (0.1005) |
| 2010 | 1.5290 (0.2417) |
| 2012 | 0.8530 (0.0604) |
| 2013 | 1.1410 (0.1269) |
| 2015 | 0.9340 (0.1972) |
| 2019 | 0.8840 (0.0770) |
