# year    value 
 1901 9.141538 
 1902 8.555519 
 1903 8.773904 
 1904 9.135666 
 1905 8.624148 
 1906 8.745519 
 1907 8.766615 
 1908  8.63423 
 1909 8.919812 
 1910 9.200587 
 1911 8.857776 
 1912 9.083155 
 1913  9.50642 
 1914 9.648918 
 1915 9.369751 
 1916 8.527081 
 1917 9.093085 
 1918 9.063863 
 1919 9.320522 
 1920  8.98982 
 1921  8.94258 
 1922 8.896916 
 1923 8.716897 
 1924 8.841892 
 1925 8.713454 
 1926 9.239897 
 1927 9.035016 
 1928 9.125954 
 1929 8.932145 
 1930 9.224692 
 1931 8.615377 
 1932 9.112805 
 1933 8.967205 
 1934   9.3105 
 1935 9.226406 
 1936 9.197895 
 1937 8.973055 
 1938 8.858486 
 1939 9.528792 
 1940  9.62225 
 1941 9.735656 
 1942 8.742137 
 1943 8.673061 
 1944  9.28863 
 1945 9.461713 
 1946 9.039547 
 1947 9.296564 
 1948 9.007463 
 1949 9.283374 
 1950 9.383399 
 1951 9.613086 
 1952 9.028647 
 1953 9.049036 
 1954 9.037073 
 1955 8.514235 
 1956 8.926061 
 1957  9.03496 
 1958 9.538203 
 1959 9.536575 
 1960   8.8567 
 1961 9.312889 
 1962 9.446569 
 1963 9.409076 
 1964 8.956635 
 1965  9.50923 
 1966 9.069674 
 1967 8.861547 
 1968 9.529139 
 1969 9.455851 
 1970 9.277005 
 1971 9.099267 
 1972 9.253454 
 1973 9.256451 
 1974 9.352682 
 1975 9.424963 
 1976 9.078824 
 1977 9.668616 
 1978 9.285204 
 1979 9.882856 
 1980 9.474566 
 1981 9.373815 
 1982 9.202532 
 1983   8.9995 
 1984 8.592403 
 1985 9.850108 
 1986  9.51881 
 1987 9.764146 
 1988 9.405483 
 1989 9.270981 
 1990   9.5434 
 1991 9.594268 
 1992  9.18301 
 1993 9.611128 
 1994  9.77787 
 1995 9.125977 
 1996 9.459954 
 1997  9.66277 
 1998 10.00599 
 1999 9.690737 
 2000 9.294734 
 2001 9.797457 
 2002 9.480092 
 2003 9.659405 
 2004 9.852421 
 2005 9.895779 
 2006 9.827594 
 2007 8.832388 
 2008 9.602075 
 2009 9.984652 
 2010 9.220278 
 2011  9.59652 
 2012 9.467161 
 2013  9.99941 
 2014 10.15571 
 2015 10.07944 
 2016 9.735558 
 2017 10.25053 
 2018 9.413952