Year | Value | 2021 | 19.602977667494 | 2020 | 19.602977667494 | 2019 | 19.602977667494 | 2018 | 19.602977667494 | 2017 | 19.602977667494 | 2016 | 19.602977667494 | 2015 | 19.602977667494 | 2014 | 19.602977667494 | 2013 | 19.602977667494 | 2012 | 19.602977667494 | 2011 | 19.602977667494 | 2010 | 19.354838709677 | 2009 | 19.354838709677 | 2008 | 19.354838709677 | 2007 | 18.858560794045 | 2006 | 18.858560794045 | 2005 | 18.858560794045 | 2004 | 18.858560794045 | 2003 | 18.610421836228 | 2002 | 18.610421836228 | 2001 | 18.362282878412 | 2000 | 17.866004962779 | 1999 | 17.866004962779 | 1998 | 17.866004962779 | 1997 | 17.866004962779 | 1996 | 17.369727047146 | 1995 | 17.369727047146 | 1994 | 17.12158808933 | 1993 | 17.12158808933 | 1992 | 17.12158808933 | 1991 | 16.873449131514 | 1990 | 16.873449131514 | 1989 | 16.625310173697 | 1988 | 16.625310173697 | 1987 | 16.129032258064 | 1986 | 16.129032258064 | 1985 | 16.129032258064 | 1984 | 16.129032258064 | 1983 | 16.129032258064 | 1982 | 16.129032258064 | 1981 | 16.129032258064 | 1980 | 16.129032258064 | 1979 | 16.129032258064 | 1978 | 16.129032258064 | 1977 | 16.129032258064 | 1976 | 16.129032258064 | 1975 | 16.129032258064 | 1974 | 16.129032258064 | 1973 | 16.129032258064 | 1972 | 16.129032258064 | 1971 | 16.129032258064 | 1970 | 16.129032258064 | 1969 | 16.129032258064 | 1968 | 16.129032258064 | 1967 | 16.129032258064 | 1966 | 16.129032258064 | 1965 | 16.129032258064 | 1964 | 16.129032258064 | 1963 | 16.129032258064 | 1962 | 16.129032258064 | 1961 | 16.129032258064 |
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