| Year | Value (SE) |
|---|---|
| 2000 | 0.6402 (0.1547) |
| 2001 | 0.0852 (0.0310) |
| 2002 | 0.6360 (0.1946) |
| 2003 | 0.5876 (0.0987) |
| 2005 | 0.4512 (0.1231) |
| 2007 | 0.6860 (0.1496) |
| 2008 | 0.8528 (0.1541) |
| 2010 | 0.4760 (0.1071) |
| 2012 | 0.6371 (0.1248) |
| 2013 | 0.7213 (0.1865) |
| 2015 | 0.5187 (0.1824) |
| 2019 | 0.6835 (0.2857) |
