1886 45.9
 1887 30.
 1888 18.4
 1889 42.3
 1890 21.9
 1891 21.1
 1892 53.9
 1893 28.1
 1894 24.300001
 1895 22.4
 1896 29.4
 1897 21.4
 1898 27.1
 1899 28.
 1900 28.9
 1901 53.
 1902 22.6
 1903 45.5
 1904 44.4
 1905 37.600002
 1906 33.5
 1907 64.200005
 1908 22.
 1909 28.7
 1910 25.6
 1911 16.800001
 1912 25.6
 1913 30.7
 1914 23.
 1915 31.1
 1916 25.9
 1917 26.9
 1918 32.100002
 1919 20.5
 1920 74.1
 1921 16.300001
 1922 33.3
 1923 25.1
 1924 29.7
 1925 27.6
 1926 23.7
 1927 34.8
 1928 30.800001
 1929 33.7
 1930 26.7
 1931 38.5
 1932 19.
 1933 21.5
 1934 24.5
 1935 38.
 1936 47.8
 1937 27.300001
 1938 36.7
 1939 37.8
 1940 49.600002
 1941 36.9
 1942 48.100002
 1943 35.3
 1944 42.9
 1945 20.7
 1946 27.6
 1947 39.
 1948 28.7
 1949 35.100002
 1950 40.4
 1951 55.5
 1952 27.1
 1953 31.800001
 1954 19.800001
 1955 76.8
 1956 21.6
 1957 30.1
 1958 26.7
 1959 25.
 1960 57.5
 1961 20.300001
 1962 18.6
 1963 30.1
 1964 29.9
 1965 38.7
 1966 55.2
 1967 30.300001
 1968 22.5
 1969 31.4
 1970 24.5
 1971 19.300001
 1972 65.8
 1973 53.
 1974 27.800001
 1975 33.3
 1976 24.1
 1977 42.2
 1978 35.8
 1979 38.5
 1980 31.300001
 1981 38.7
 1982 30.1
 1983 29.
 1984 29.4
 1985 23.
 1986 19.7
 1987 95.700005
 1988 46.
 1989 39.4
 1990 37.4
 1991 25.800001
 1992 68.200005
 1993 38.8
 1994 33.
 1995 82.
 1996 24.4
 1997 50.600002
 1998 32.4
 1999 26.2
 2000 47.
 2001 104.200005
 2002 26.6
 2003 26.4
 2004 25.800001
 2005 21.
 2006 19.
 2007 60.