| Year | Value (SE) |
|---|---|
| 2000 | 0.6620 (0.0812) |
| 2001 | 0.2490 (0.0283) |
| 2002 | 0.5840 (0.0747) |
| 2003 | 0.6970 (0.0780) |
| 2005 | 0.8900 (0.1157) |
| 2007 | 0.8840 (0.1297) |
| 2008 | 0.7320 (0.0914) |
| 2010 | 0.5260 (0.0956) |
| 2012 | 0.7760 (0.1093) |
| 2013 | 0.6710 (0.1120) |
| 2015 | 0.9750 (0.2336) |
| 2019 | 1.5750 (0.5844) |
