| Year | Value (SE) |
|---|---|
| 2000 | 0.2812 (0.0374) |
| 2001 | 0.0842 (0.0099) |
| 2002 | 0.3544 (0.0501) |
| 2003 | 0.4874 (0.0591) |
| 2005 | 0.5833 (0.0763) |
| 2007 | 0.6634 (0.1033) |
| 2008 | 0.6627 (0.0860) |
| 2010 | 0.6195 (0.1188) |
| 2012 | 0.6062 (0.0897) |
| 2013 | 0.6708 (0.1220) |
| 2015 | 0.8334 (0.2278) |
| 2019 | 1.1438 (0.4309) |
