Year Years 1800 449.3 1950 235.4 1951 233.1 1952 228.1 1953 223.8 1954 218.3 1955 212.7 1965 97.7 1966 94.7 1967 92.1 1968 89.9 1969 88.5 1970 87.9 1971 87.8 1972 88.2 1973 88.9 1974 89.6 1975 90.3 1976 90.7 1977 91.1 1978 91.4 1979 92.1 1980 93 1981 94.2 1982 95.7 1983 97.8 1984 100 1985 102.2 1986 104.4 1987 106.4 1988 108.1 1989 109.4 1990 110.4 1991 110.8 1992 110.7 1993 109.9 1994 108.3 1995 106.1 1996 103.4 1997 100.2 1998 96.7 1999 93.1 2000 89.3 2001 85.4 2002 81.5 2003 77.6 2004 73.9 2005 70.3 2006 67 2007 64 2008 61.4 2009 59 2010 56.7 2011 54.6 2012 52.8 2013 51