Year Years 1800 453.1 1950 261.7 1951 259.2 1952 253.9 1953 249.3 1963 180.9 1964 173.8 1965 167.1 1966 161 1967 155.2 1968 149.7 1969 144.8 1970 140.4 1971 136.4 1972 133 1973 130.2 1974 128 1975 126.3 1976 124.9 1977 123.9 1978 123.1 1979 122.3 1980 121.7 1981 121 1982 119.8 1983 118.1 1984 116.3 1985 113.8 1986 110.8 1987 107.3 1988 103.5 1989 99.4 1990 95.4 1991 91.8 1992 88.5 1993 85.8 1994 83.4 1995 81.3 1996 79.1 1997 77 1998 74.9 1999 72.9 2000 71 2001 69.4 2002 68 2003 67 2004 66.2 2005 65.7 2006 65.3 2007 65 2008 64.5 2009 63.7 2010 62.5 2011 61.1 2012 59.7 2013 58.2