| Year | Value | | 2020 | 0.39671205052525 | | 2019 | 0.4000084001764 | | 2018 | 0.4062145408557 | | 2017 | 0.41275608935619 | | 2016 | 0.42170383107388 | | 2015 | 0.43098773049763 | | 2014 | 0.44075856017401 | | 2013 | 0.45233961356627 | | 2012 | 0.46457157789801 | | 2011 | 0.4775471269372 | | 2010 | 0.49126309062617 | | 2009 | 0.50561485294192 | | 2008 | 0.52055588427696 | | 2007 | 0.62534002864057 | | 2006 | 0.64382142968826 | | 2005 | 0.66265758825771 | | 2004 | 0.68139319599691 | | 2003 | 0.70023142648645 | | 2002 | 0.71986318485984 | | 2001 | 0.846285020332 | | 2000 | 0.87140179138423 | | 1999 | 0.89833387139789 | | 1998 | 0.98489518397842 | | 1997 | 1.0201552676317 | | 1996 | 1.0579593706262 | | 1995 | 0.77594468031726 | | 1994 | 0.93552308102499 | | 1993 | 1.034475624306 | | 1992 | 1.0651094293428 | | 1991 | 1.4632279833572 |
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