Year Years 1800 472.3 1950 156.8 1951 154.2 1952 149.4 1953 145.2 1954 140.2 1955 135.8 1956 131.3 1957 126.7 1958 122 1959 118.2 1960 113.7 1961 109.9 1962 106.2 1963 102.6 1964 99.02 1965 95.49 1966 92.02 1967 89.12 1968 85.86 1969 83.28 1970 80.85 1971 78.05 1972 75.9 1973 73.88 1974 72.33 1984 25.8 1985 25.3 1986 24.8 1987 24.2 1988 23.6 1989 23 1990 22.2 1991 21.4 1992 20.6 1993 19.9 1994 19.1 1995 18.4 1996 17.8 1997 17.2 1998 16.7 1999 16.3 2000 15.9 2001 15.5 2002 15.2 2003 14.9 2004 14.6 2005 14.4 2006 14.1 2007 13.8 2008 13.5 2009 13.2 2010 12.8 2011 12.5 2012 12.2 2013 11.8