# year    value 
 1901 10.28165 
 1902 9.357514 
 1903 9.429556 
 1904 10.31332 
 1905 9.126541 
 1906 9.318855 
 1907 9.925982 
 1908   8.9268 
 1909 9.725581 
 1910 10.30546 
 1911 8.346604 
 1912  8.31076 
 1913 9.476419 
 1914 10.04099 
 1915 9.433618 
 1916 8.204972 
 1917 10.67997 
 1918 9.644886 
 1919  8.24766 
 1920 8.613319 
 1921  10.1074 
 1922 9.686954 
 1923 9.389187 
 1924 9.478428 
 1925 8.668253 
 1926 10.02663 
 1927 10.13554 
 1928 9.759828 
 1929 9.097681 
 1930 8.858117 
 1931 9.238893 
 1932 10.12752 
 1933 10.91189 
 1934 10.59227 
 1935 9.223664 
 1936 9.460476 
 1937 10.86748 
 1938 9.550977 
 1939 10.30397 
 1940 9.744981 
 1941 9.090547 
 1942 10.03232 
 1943 10.45345 
 1944 10.11021 
 1945 9.829943 
 1946 8.481072 
 1947 9.767983 
 1948 9.360113 
 1949  10.5239 
 1950  10.6057 
 1951 9.308055 
 1952 10.06046 
 1953 10.92446 
 1954 10.59456 
 1955 9.518771 
 1956 9.544031 
 1957 8.952242 
 1958  10.3065 
 1959 9.355608 
 1960 10.19757 
 1961  8.29143 
 1962 10.80025 
 1963 11.36661 
 1964 9.462138 
 1965 10.02671 
 1966 10.42823 
 1967 10.85751 
 1968 9.524758 
 1969 9.444418 
 1970 8.780703 
 1971 8.520317 
 1972 8.729338 
 1973  9.46806 
 1974  10.1664 
 1975 9.342286 
 1976 9.751346 
 1977 10.17062 
 1978 9.473228 
 1979 10.19031 
 1980 10.08397 
 1981 10.21915 
 1982 8.703519 
 1983  10.2239 
 1984 8.775295 
 1985 7.776524 
 1986 8.958155 
 1987 10.60081 
 1988 10.63415 
 1989 10.07286 
 1990 10.64191 
 1991 10.10301 
 1992 9.819009 
 1993 9.047628 
 1994 9.422722 
 1995 11.11361 
 1996 9.673012 
 1997 10.18242 
 1998 10.45363 
 1999 10.67935 
 2000  8.52384 
 2001 11.11115 
 2002 9.531121 
 2003 10.34849 
 2004 9.711201 
 2005 10.40898 
 2006  9.69834 
 2007 10.35739 
 2008 10.71122 
 2009 10.13643 
 2010 10.38878 
 2011 10.49533 
 2012 11.15868 
 2013 10.02526 
 2014 11.15522 
 2015 11.17516 
 2016 11.47065 
 2017 10.96238 
 2018 10.09953