# year    value 
 1901 9.785727 
 1902  9.11902 
 1903 9.013049 
 1904 9.474849 
 1905 9.451518 
 1906 8.621727 
 1907 8.622895 
 1908 9.243095 
 1909 8.843066 
 1910 9.052406 
 1911 8.523868 
 1912 8.546695 
 1913 9.549147 
 1914 9.648665 
 1915 9.070246 
 1916 7.646219 
 1917  8.65582 
 1918 9.524963 
 1919 8.854465 
 1920 8.335315 
 1921 7.840594 
 1922  8.74092 
 1923 8.800425 
 1924 8.836872 
 1925  9.09715 
 1926 9.513308 
 1927 8.896186 
 1928 8.843554 
 1929 8.987094 
 1930 9.295912 
 1931 8.685465 
 1932 9.522712 
 1933 8.873705 
 1934 9.485706 
 1935 9.265515 
 1936 8.974821 
 1937 9.618741 
 1938 8.901373 
 1939 10.12183 
 1940 9.864067 
 1941 9.655279 
 1942 8.621135 
 1943 9.402817 
 1944 10.13073 
 1945 9.847562 
 1946 8.937326 
 1947 8.822611 
 1948 9.153969 
 1949 8.596001 
 1950 8.990759 
 1951 9.556257 
 1952  8.32725 
 1953 9.029966 
 1954 8.435143 
 1955 8.276797 
 1956 8.154194 
 1957 8.850991 
 1958 9.397001 
 1959 9.028274 
 1960 8.929432 
 1961 9.298934 
 1962 8.393096 
 1963 9.684432 
 1964 8.355614 
 1965 9.893966 
 1966 8.948354 
 1967 8.378145 
 1968 9.394037 
 1969 9.425294 
 1970 8.927977 
 1971 8.821176 
 1972 9.646062 
 1973  8.63544 
 1974 8.743793 
 1975  8.65918 
 1976 8.919331 
 1977 9.194718 
 1978 8.973058 
 1979 9.546245 
 1980 9.214519 
 1981 8.869777 
 1982 9.410985 
 1983 9.219312 
 1984 8.511198 
 1985 9.103778 
 1986 9.413555 
 1987 9.907761 
 1988 8.693892 
 1989 9.307127 
 1990 9.011456 
 1991  9.41125 
 1992 9.163609 
 1993 9.524619 
 1994 9.761219 
 1995  9.38111 
 1996 8.788301 
 1997 10.20166 
 1998 10.00362 
 1999  8.83086 
 2000 8.862202 
 2001 9.234708 
 2002 8.966185 
 2003  9.10063 
 2004 9.205875 
 2005 9.444262 
 2006 9.943851 
 2007 8.073212 
 2008 9.334017 
 2009 9.290648 
 2010 8.773096 
 2011 9.189012 
 2012 9.365023 
 2013 8.941306 
 2014 9.863275 
 2015 10.22765 
 2016 9.449032 
 2017 9.781899 
 2018 8.527918