# year    value 
 1901 9.329175 
 1902 9.348763 
 1903 8.427372 
 1904 9.179589 
 1905 9.442412 
 1906 8.553798 
 1907 8.588933 
 1908 9.158143 
 1909 8.066399 
 1910 11.49349 
 1911  9.64109 
 1912 7.865764 
 1913 8.594651 
 1914 9.815975 
 1915 9.017541 
 1916 9.390764 
 1917 6.970391 
 1918 9.427549 
 1919 9.136385 
 1920 7.918036 
 1921 9.455917 
 1922 8.407717 
 1923 8.422004 
 1924 8.163918 
 1925 10.68326 
 1926 9.928788 
 1927 9.088895 
 1928 9.884715 
 1929 8.966892 
 1930  9.62532 
 1931  9.36799 
 1932 8.932104 
 1933 8.720832 
 1934 11.86794 
 1935 8.435383 
 1936 10.28177 
 1937  9.24256 
 1938 9.585908 
 1939 10.41484 
 1940 10.15346 
 1941 9.632387 
 1942 9.067213 
 1943  9.32911 
 1944  8.47054 
 1945 8.768585 
 1946  10.5736 
 1947 9.353873 
 1948 8.709906 
 1949 9.859321 
 1950 8.433863 
 1951  8.44539 
 1952 8.785595 
 1953 8.614663 
 1954  9.16876 
 1955 8.741051 
 1956 9.408936 
 1957 8.947521 
 1958 9.126959 
 1959 9.544684 
 1960 9.074066 
 1961 9.374207 
 1962 9.107147 
 1963 9.973402 
 1964 8.587923 
 1965 8.133661 
 1966 9.869022 
 1967 8.996774 
 1968 9.261376 
 1969  9.12303 
 1970 8.303146 
 1971 8.894367 
 1972 10.34512 
 1973  9.07564 
 1974 9.951671 
 1975 7.621914 
 1976 9.237066 
 1977 9.966358 
 1978 9.783358 
 1979 9.012665 
 1980 9.228687 
 1981 10.41984 
 1982 8.840969 
 1983 8.504516 
 1984 9.326756 
 1985 10.53096 
 1986 10.88564 
 1987  10.6405 
 1988 10.11586 
 1989 10.44931 
 1990  10.1231 
 1991 9.575826 
 1992 11.27812 
 1993 9.976453 
 1994 10.93255 
 1995  8.95628 
 1996 9.499295 
 1997 9.242358 
 1998  9.22796 
 1999 9.221407 
 2000 10.79308 
 2001 10.20322 
 2002 8.697449 
 2003 9.921587 
 2004 11.07529 
 2005 10.06356 
 2006 10.71908 
 2007 10.83438 
 2008 9.220631 
 2009 9.732819 
 2010 9.528361 
 2011 9.289131 
 2012  11.6985 
 2013 9.534122 
 2014 10.16607 
 2015 10.82707 
 2016 11.04977 
 2017 10.90167 
 2018 10.58393