# year value 1900 2.554304 1901 2.510437 1902 2.522787 1903 2.240111 1904 2.273801 1905 2.376396 1906 2.425302 1907 2.471217 1908 2.489048 1909 2.492253 1910 2.539842 1911 2.515424 1912 2.594377 1913 2.457091 1914 2.515671 1915 2.588124 1916 2.631912 1917 2.613633 1918 2.586622 1919 2.594566 1920 2.666291 1921 2.669166 1922 2.694389 1923 2.684072 1924 2.679454 1925 2.691702 1926 2.67873 1927 2.712149 1928 2.719594 1929 2.678396 1930 2.637543 1931 2.661068 1932 2.684094 1933 2.637838 1934 2.6056 1935 2.719966 1936 2.794217 1937 2.725916 1938 2.754702 1939 2.78247 1940 2.706905 1941 2.734089 1942 2.772447 1943 2.809214 1944 2.822436 1945 2.734655 1946 2.744759 1947 2.747983 1948 2.807137 1949 2.817453 1950 2.778865 1951 2.798177 1952 2.783261 1953 2.74833 1954 2.759014 1955 2.783916 1956 2.808969 1957 2.77988 1958 2.804751 1959 2.82646 1960 2.826058 1961 2.778014 1962 2.75255 1963 2.645028 1964 2.513956 1965 2.560546 1966 2.60781 1967 2.638341 1968 2.634271 1969 2.633564 1970 2.690746 1971 2.795311 1972 2.846267 1973 2.836707 1974 2.795444 1975 2.802238 1976 2.831981 1977 2.822686 1978 2.890475 1979 2.911537 1980 3.002277 1981 3.002049 1982 2.837189 1983 2.766122 1984 2.884812 1985 2.884998 1986 2.943232 1987 3.033422 1988 3.089911 1989 3.119483 1990 3.178841 1991 3.093323 1992 2.791096 1993 2.963816 1994 2.948667 1995 3.057687 1996 3.183174 1997 3.283192 1998 3.274696 1999 3.332816 2000 3.310129 2001 3.410497 2002 3.474052 2003 3.398961 2004 3.455836 2005 3.519518