| Year | Value | | 2020 | 0.64172650248781 | | 2019 | 0.57727570045058 | | 2018 | 0.62861004834969 | | 2017 | 0.61886873300552 | | 2016 | 0.62733471233096 | | 2015 | 0.63737465597321 | | 2014 | 0.65057425447007 | | 2013 | 0.6363338349053 | | 2012 | 0.65539708317988 | | 2011 | 0.67618515263914 | | 2010 | 0.69527690799178 | | 2009 | 0.7068514240281 | | 2008 | 0.66101700131393 | | 2007 | 0.62876011188061 | | 2006 | 0.62831764338158 | | 2005 | 0.4730534384353 | | 2004 | 0.48680562513252 | | 2003 | 0.50399543743169 | | 2002 | 0.51795756067201 | | 2001 | 0.52492947515836 | | 2000 | 0.54128221107792 | | 1999 | 0.51513823713458 | | 1998 | 0.51039140788837 | | 1997 | 0.5200670470437 | | 1996 | 0.54468134292389 | | 1995 | 0.55593886249143 | | 1994 | 0.52867787451677 | | 1993 | 0.54311865559822 | | 1992 | 0.56363910658242 | | 1991 | 0.58512103412486 |
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