| Year | Value | | 2020 | 0.7619857203876 | | 2019 | 0.71709096634868 | | 2018 | 0.72832534150496 | | 2017 | 0.70547685553194 | | 2016 | 0.71599944384657 | | 2015 | 0.7252380948215 | | 2014 | 0.73760218381206 | | 2013 | 0.72844354154164 | | 2012 | 0.73790296474659 | | 2011 | 0.74330394080272 | | 2010 | 0.73960627358364 | | 2009 | 0.73663122171808 | | 2008 | 0.75850846348688 | | 2007 | 0.76937688763445 | | 2006 | 0.81314083033002 | | 2005 | 0.73471625345628 | | 2004 | 0.77140710292347 | | 2003 | 0.77562850795621 | | 2002 | 0.79012544133383 | | 2001 | 0.81794756785988 | | 2000 | 0.83840739807101 | | 1999 | 0.86421394166638 | | 1998 | 0.92287504768386 | | 1997 | 0.94872138557812 | | 1996 | 0.95639500631402 | | 1995 | 0.95393339846132 | | 1994 | 0.42634504118587 | | 1993 | 0.43826865993227 | | 1992 | 0.45084683505369 | | 1991 | 0.46235894310263 | | 1990 | 0.47403625496768 |
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