| Year | Value | | 2020 | 0.66363801937971 | | 2019 | 0.58350227547653 | | 2018 | 0.57700736676408 | | 2017 | 0.58073189640904 | | 2016 | 0.57417508971259 | | 2015 | 0.57835844722616 | | 2014 | 0.57857484422283 | | 2013 | 0.58316160419847 | | 2012 | 0.58495071282795 | | 2011 | 0.59041530594874 | | 2010 | 0.58731468677046 | | 2009 | 0.61700494133955 | | 2008 | 0.63211430708931 | | 2007 | 0.64003204678107 | | 2006 | 0.64008168948432 | | 2005 | 0.75288165453272 | | 2004 | 0.749994000048 | | 2003 | 0.82879161805364 | | 2002 | 1.1781841475132 | | 2001 | 1.4392872741044 | | 2000 | 1.5975407179007 | | 1999 | 1.8652597338823 | | 1998 | 1.9102276490445 | | 1997 | 1.7913112477683 | | 1996 | 1.8514516016248 | | 1995 | 2.0573724529931 | | 1994 | 1.9142700277447 | | 1993 | 1.3094183286029 |
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