# year    value 
 1901 8.749556 
 1902 8.411824 
 1903 8.494871 
 1904 8.659933 
 1905 8.679772 
 1906 8.581803 
 1907 8.564775 
 1908 8.489651 
 1909 8.667463 
 1910  8.45729 
 1911 8.598584 
 1912 8.001028 
 1913 8.619967 
 1914 8.572972 
 1915 8.573806 
 1916 8.504876 
 1917 8.573182 
 1918 8.681536 
 1919 8.567154 
 1920 8.436347 
 1921 8.633968 
 1922 8.542373 
 1923 8.819051 
 1924 8.771751 
 1925 9.007908 
 1926 9.065906 
 1927 9.180144 
 1928   8.8143 
 1929 8.820346 
 1930 8.774443 
 1931 8.926976 
 1932  9.02555 
 1933 8.925961 
 1934 8.796948 
 1935 8.709923 
 1936 8.967133 
 1937 9.081964 
 1938 9.093467 
 1939 8.888546 
 1940 8.837382 
 1941  8.82585 
 1942 9.118064 
 1943  9.14482 
 1944 8.992102 
 1945 9.212974 
 1946 8.894543 
 1947 9.120242 
 1948 8.771459 
 1949 8.951518 
 1950  8.32258 
 1951 9.109479 
 1952 8.575759 
 1953 8.941425 
 1954 9.048232 
 1955 8.660079 
 1956  8.37499 
 1957 8.827114 
 1958 8.786231 
 1959 8.780666 
 1960 8.743691 
 1961 8.648215 
 1962 8.762185 
 1963   9.1443 
 1964 8.513017 
 1965 8.676652 
 1966 8.691239 
 1967 8.727349 
 1968  8.55727 
 1969 8.764722 
 1970 8.557463 
 1971 8.804014 
 1972 8.470965 
 1973 8.785798 
 1974 8.535862 
 1975 8.755074 
 1976 8.443238 
 1977 8.942143 
 1978 8.983684 
 1979 8.920362 
 1980 9.111573 
 1981 8.727722 
 1982 8.620596 
 1983 9.299686 
 1984 8.607916 
 1985 8.650346 
 1986 8.774726 
 1987 8.993807 
 1988 9.335992 
 1989 9.025574 
 1990 9.359045 
 1991 9.132599 
 1992 8.551788 
 1993 8.808752 
 1994  9.28535 
 1995 9.602608 
 1996 8.776863 
 1997 9.217321 
 1998 9.453683 
 1999 9.349729 
 2000 8.790411 
 2001 9.571789 
 2002 9.412931 
 2003  9.52837 
 2004 9.489031 
 2005 9.806658 
 2006 9.634583 
 2007 9.658901 
 2008  9.66137 
 2009 9.462845 
 2010 9.799424 
 2011 9.476805 
 2012 9.593108 
 2013 9.629158 
 2014 9.790277 
 2015 9.844736 
 2016 9.644427 
 2017 9.740954 
 2018 9.757456