| Year | Value (SE) |
|---|---|
| 2000 | 0.4687 (0.0612) |
| 2001 | 0.1574 (0.0184) |
| 2002 | 0.5034 (0.0680) |
| 2003 | 0.6273 (0.0736) |
| 2005 | 0.7672 (0.0999) |
| 2007 | 0.7929 (0.1195) |
| 2008 | 0.8191 (0.1044) |
| 2010 | 0.8043 (0.1507) |
| 2012 | 0.6619 (0.0965) |
| 2013 | 0.7656 (0.1322) |
| 2015 | 0.9106 (0.2361) |
| 2019 | 1.3923 (0.5209) |
