# year    value 
 1901 9.909606 
 1902 9.302767 
 1903 9.670141 
 1904 10.80703 
 1905 9.887521 
 1906 9.883667 
 1907 9.173267 
 1908 9.726607 
 1909 9.680238 
 1910 9.761711 
 1911 9.990266 
 1912 10.52841 
 1913 10.63101 
 1914 10.65106 
 1915 10.10187 
 1916 10.93546 
 1917 9.150591 
 1918 10.77238 
 1919 9.027302 
 1920 12.29957 
 1921 10.81812 
 1922 10.57593 
 1923 10.52069 
 1924 10.43578 
 1925 9.729399 
 1926 10.34559 
 1927  10.9273 
 1928 9.519009 
 1929 9.425228 
 1930  10.6048 
 1931 9.572672 
 1932 8.875151 
 1933 9.895945 
 1934  11.8872 
 1935 9.065098 
 1936 10.98321 
 1937 10.73767 
 1938 9.631338 
 1939 9.361192 
 1940 9.807207 
 1941 9.043496 
 1942 10.23772 
 1943 11.47218 
 1944 9.592859 
 1945 12.02831 
 1946 11.98218 
 1947 12.01895 
 1948 11.98964 
 1949 10.46724 
 1950  11.2719 
 1951 9.890535 
 1952 11.01907 
 1953 11.08637 
 1954  9.86784 
 1955 9.072508 
 1956 9.536823 
 1957 10.38124 
 1958  9.38026 
 1959 11.48167 
 1960 10.76186 
 1961 11.64595 
 1962 8.975235 
 1963 10.13179 
 1964 10.37012 
 1965 9.472566 
 1966 10.82981 
 1967 10.57292 
 1968 10.93549 
 1969 10.32457 
 1970 8.724392 
 1971 10.19007 
 1972 10.71453 
 1973  9.66507 
 1974 10.50427 
 1975 10.41927 
 1976   9.8477 
 1977 10.65625 
 1978 9.691066 
 1979 10.35466 
 1980 9.019652 
 1981 11.35175 
 1982 10.08879 
 1983 10.91965 
 1984 9.057605 
 1985 10.23683 
 1986 10.70986 
 1987 8.817252 
 1988 10.66616 
 1989 11.74734 
 1990 11.71214 
 1991 10.03081 
 1992 11.33407 
 1993 11.27372 
 1994 11.65484 
 1995 10.38905 
 1996 10.16294 
 1997 10.97009 
 1998 11.11535 
 1999 11.83517 
 2000 12.32028 
 2001 11.86698 
 2002 11.83497 
 2003 11.97247 
 2004 10.38055 
 2005 10.95096 
 2006 10.62317 
 2007 12.96373 
 2008 11.31588 
 2009 12.40228 
 2010 10.86006 
 2011 12.63128 
 2012 12.26243 
 2013 10.38939 
 2014 12.36623 
 2015 11.78158 
 2016 11.34324 
 2017  12.4741 
 2018 12.66645