| Year | Value | | 2019 | 1.248987063106 | | 2018 | 1.1686577608589 | | 2017 | 0.85167229869129 | | 2016 | 0.34866364550702 | | 2015 | 0.24478603366127 | | 2014 | 0.72980067103826 | | 2013 | 0.94766118367524 | | 2012 | 0.79981424820506 | | 2011 | 0.40858075225803 | | 2010 | 0.092362761285288 | | 2009 | 0.49308004122116 | | 2008 | 0.77491162676383 | | 2007 | 0.85664320381861 | | 2006 | 0.79068182187254 | | 2005 | 0.68316669098133 | | 2004 | 0.62960965115222 | | 2003 | 0.57096690552318 | | 2002 | 0.54174878965863 | | 2001 | 0.52326292659438 | | 2000 | 0.50241849309132 | | 1999 | 0.46269245690888 | | 1998 | 0.42654117579316 | | 1997 | 0.35875035884347 | | 1996 | 0.30897454475862 | | 1995 | 0.24724212578995 | | 1994 | 0.19028108785733 | | 1993 | 0.1654831857145 | | 1992 | 0.16050778446589 | | 1991 | 0.18600746239991 | | 1990 | 0.22957044623319 | | 1989 | 0.27449051767568 | | 1988 | 0.28584757330911 | | 1987 | 0.24733438294357 | | 1986 | 0.20427277509126 | | 1985 | 0.11508707393334 | | 1984 | 0.062927629971631 | | 1983 | 0.093931799616092 | | 1982 | 0.24806214270763 | | 1981 | 0.47000837677159 | | 1980 | 0.75902307297759 | | 1979 | 1.0163320109397 | | 1978 | 1.1695653338372 | | 1977 | 1.1576279510303 | | 1976 | 1.0318195535123 | | 1975 | 0.83684399683527 | | 1974 | 0.71042557479799 | | 1973 | 0.73751668803327 | | 1972 | 0.95913947802992 | | 1971 | 1.3518015681629 | | 1970 | 1.7894572204498 | | 1969 | 2.1668104071796 | | 1968 | 2.5609114295883 | | 1967 | 2.8987909037523 | | 1966 | 3.2110543527368 | | 1965 | 3.5654009917221 | | 1964 | 3.9231306872711 | | 1963 | 4.0622080223029 | | 1962 | 3.8789010471983 | | 1961 | 3.4131589470552 |
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