| Year | Value (SE) |
|---|---|
| 2002 | 0.5127 (0.0535) |
| 2003 | 0.6456 (0.0665) |
| 2004 | 0.3954 (0.0877) |
| 2006 | 0.7220 (0.0350) |
| 2008 | 0.7679 (0.0702) |
| 2009 | 0.8121 (0.0570) |
| 2010 | 0.8251 (0.1530) |
| 2011 | 0.8713 (0.0831) |
| 2013 | 0.6599 (0.1107) |
| 2014 | 0.6685 (0.1101) |
| 2016 | 0.6739 (0.0668) |
| 2019 | 0.8469 (0.1375) |
