| Year | Value | | 2020 | 0.93603315448564 | | 2019 | 0.90285601239037 | | 2018 | 0.9215357858879 | | 2017 | 0.92018726999575 | | 2016 | 0.91075453979028 | | 2015 | 0.91522325071386 | | 2014 | 0.91819913110639 | | 2013 | 0.88113266535878 | | 2012 | 0.88740687644649 | | 2011 | 0.89980707518823 | | 2010 | 0.90945112601518 | | 2009 | 0.93096830237795 | | 2008 | 0.93275263271501 | | 2007 | 0.95329656838749 | | 2006 | 0.95448966289119 | | 2005 | 0.85836964865171 | | 2004 | 0.88007312818073 | | 2003 | 0.90869835325825 | | 2002 | 0.91962233537709 | | 2001 | 0.93870834327773 | | 2000 | 0.95238063629765 | | 1999 | 0.9630680185422 | | 1998 | 0.99625368018783 | | 1997 | 1.03355261694 | | 1996 | 1.074329452938 | | 1995 | 1.0795083009455 | | 1994 | 0.7393119964693 | | 1993 | 0.77834813909177 | | 1992 | 0.80088881230648 | | 1991 | 0.89190557005985 |
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