| Year | Value (SE) |
|---|---|
| 2000 | 0.4990 (0.0473) |
| 2002 | 0.5580 (0.0171) |
| 2003 | 0.4920 (0.0147) |
| 2004 | 0.4590 (0.0305) |
| 2005 | 0.5610 (0.0395) |
| 2006 | 0.5100 (0.0147) |
| 2007 | 0.6130 (0.0078) |
| 2008 | 0.4800 (0.0291) |
| 2009 | 0.4270 (0.0248) |
| 2010 | 0.7710 (0.0339) |
| 2011 | 0.4360 (0.0215) |
| 2012 | 0.5010 (0.0157) |
| 2013 | 0.5890 (0.0310) |
| 2014 | 0.7020 (0.0360) |
| 2015 | 0.4170 (0.0383) |
| 2016 | 0.4410 (0.0197) |
| 2017 | 0.1960 (0.0122) |
| 2020 | 0.5080 (0.0332) |
| 2021 | 0.5830 (0.0751) |
| 2022 | 0.5280 (0.1012) |
| 2023 | 0.4510 (0.0276) |
