| Year | Value (SE) |
|---|---|
| 2000 | 0.3225 (0.0428) |
| 2001 | 0.1065 (0.0125) |
| 2002 | 0.4475 (0.0631) |
| 2003 | 0.5470 (0.0663) |
| 2005 | 0.7027 (0.0917) |
| 2007 | 0.6954 (0.1083) |
| 2008 | 0.7356 (0.0954) |
| 2010 | 0.7254 (0.1390) |
| 2012 | 0.6540 (0.0967) |
| 2013 | 0.6048 (0.1101) |
| 2015 | 0.9817 (0.2682) |
| 2019 | 1.2419 (0.4677) |
