Year Years 1800 469.8 1906 682.1 1907 490.4 1908 518 1909 409.3 1910 435.2 1911 427.1 1912 675.6 1913 394.8 1914 654.5 1915 313.9 1916 393.2 1917 469.3 1918 333.4 1919 571.6 1920 438.5 1921 651.2 1922 304.1 1923 597.6 1924 483.9 1925 506.7 1926 509.9 1927 326.9 1928 537.5 1929 388.4 1930 375.4 1931 483.9 1932 322 1933 381.9 1934 415.7 1935 357.7 1936 322 1937 352.8 1938 359.3 1939 315.5 1940 292.6 1941 364.1 1942 284.4 1943 266.8 1944 277.8 1945 240.7 1946 260.2 1947 270.1 1948 249.7 1949 203.5 1950 196 1951 216.6 1952 233.3 1953 222.2 1954 167.6 1955 145.1 1956 126.4 1957 111.4 1958 99.7 1959 90.7 1960 83.7 1961 77.9 1962 73 1963 68.6 1964 64.7 1965 61.2 1966 58.2 1967 55.5 1968 53 1969 50.5 1970 48.1 1971 45.7 1972 43.3 1973 41 1974 38.8 1975 36.7 1976 34.6 1977 32.6 1978 30.7 1979 28.9 1980 27.3 1981 25.9 1982 24.6 1983 23.6 1984 22.7 1985 21.9 1986 21.1 1987 20.4 1988 19.6 1989 18.8 1990 18.1 1991 17.4 1992 16.8 1993 16.3 1994 16 1995 15.8 1996 15.8 1997 15.9 1998 16 1999 16.2 2000 16.4 2001 16.5 2002 16.6 2003 16.5 2004 16.2 2005 16 2006 15.7 2007 15.4 2008 15.1 2009 15 2010 14.8 2011 14.7 2012 14.6 2013 14.4