| Year | Value (SE) |
|---|---|
| 2000 | 0.8612 (0.1093) |
| 2001 | 0.7715 (0.0136) |
| 2002 | 0.9603 (0.0338) |
| 2003 | 0.8362 (0.0647) |
| 2004 | 0.8501 (0.0505) |
| 2005 | 0.8181 (0.0307) |
| 2006 | 0.8480 (0.0437) |
| 2007 | 0.9265 (0.0570) |
| 2008 | 0.9212 (0.0500) |
| 2009 | 1.0369 (0.0624) |
| 2010 | 1.0864 (0.1640) |
| 2011 | 0.9582 (0.0585) |
| 2012 | 0.7926 (0.0433) |
| 2013 | 0.9498 (0.0914) |
| 2014 | 0.9645 (0.0734) |
| 2015 | 1.0764 (0.2516) |
| 2016 | 0.8348 (0.0415) |
| 2019 | 0.8978 (0.0907) |
| 2020 | 1.1491 (0.2403) |
| 2021 | 1.8408 (1.9763) |
| 2022 | 0.7984 (0.1610) |
| 2023 | 0.8635 (0.1070) |
