| Year | Value | | 2020 | 0.66555905257824 | | 2019 | 0.66346393595197 | | 2018 | 0.66513204763798 | | 2017 | 0.67558936923991 | | 2016 | 0.69609642706074 | | 2015 | 0.71482085144877 | | 2014 | 0.73169637302952 | | 2013 | 0.74442853318893 | | 2012 | 0.70728665776455 | | 2011 | 0.77094538316715 | | 2010 | 0.65121382129575 | | 2009 | 0.66491400838081 | | 2008 | 0.69475308574583 | | 2007 | 0.70979143083001 | | 2006 | 0.72535597880883 | | 2005 | 1.0167934021971 | | 2004 | 1.0394213541321 | | 2003 | 1.1239510626355 | | 2002 | 1.1562290232755 | | 2001 | 1.1901784771808 | | 2000 | 1.2844616321113 | | 1999 | 1.0222917080645 | | 1998 | 1.0601149504255 | | 1997 | 1.3383609768922 | | 1996 | 1.5407240639556 | | 1995 | 1.5837572103 | | 1994 | 0.98102382531774 | | 1993 | 1.3068797118211 | | 1992 | 1.3464839936715 | | 1991 | 1.3570816306693 |
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