| Year | Value (SE) |
|---|---|
| 2000 | 0.3118 (0.0770) |
| 2001 | 0.0364 (0.0133) |
| 2002 | 0.4874 (0.1519) |
| 2003 | 0.4611 (0.0804) |
| 2005 | 0.3563 (0.0973) |
| 2007 | 0.5396 (0.1210) |
| 2008 | 0.8569 (0.1577) |
| 2010 | 0.6565 (0.1530) |
| 2012 | 0.5369 (0.1079) |
| 2013 | 0.6502 (0.1746) |
| 2015 | 0.5223 (0.1961) |
| 2019 | 0.5390 (0.2279) |
