Data Table
| Year | Value (SE) |
| 2000 | 1.0349 (0.2306) |
| 2001 | 0.4471 (0.0466) |
| 2002 | 0.7804 (0.1373) |
| 2003 | 0.7853 (0.0605) |
| 2004 | 0.5710 (0.1225) |
| 2005 | 0.6772 (0.0545) |
| 2006 | 0.6383 (0.0514) |
| 2007 | 0.8722 (0.0365) |
| 2008 | 0.7921 (0.0669) |
| 2009 | 0.7065 (0.0624) |
| 2010 | 0.7903 (0.0894) |
| 2011 | 0.8527 (0.0849) |
| 2012 | 0.8269 (0.0388) |
| 2013 | 0.9819 (0.0859) |
| 2014 | 0.8732 (0.0671) |
| 2015 | 0.6152 (0.0859) |
| 2016 | 0.6245 (0.0483) |
| 2017 | 0.7229 (0.0589) |
| 2018 | 0.6323 (0.0655) |
| 2019 | 0.6481 (0.0627) |
| 2020 | 0.6542 (0.0929) |
| 2021 | 0.7452 (0.3329) |
| 2022 | 0.6825 (0.1610) |
| 2023 | 0.6378 (0.0781) |
| 2024 | 0.6725 (0.3526) |