# year    value 
 1901 3.978931 
 1902 5.324366 
 1903 4.706641 
 1904 4.177278 
 1905 4.159774 
 1906 4.043502 
 1907 4.963391 
 1908 4.393759 
 1909 4.555745 
 1910 4.823818 
 1911  4.13224 
 1912 4.930406 
 1913 4.427985 
 1914 5.684986 
 1915 4.421942 
 1916 4.947443 
 1917 4.499933 
 1918 4.010012 
 1919 3.711507 
 1920 4.283776 
 1921 4.445959 
 1922 4.838716 
 1923 4.392313 
 1924  4.80321 
 1925 3.905701 
 1926 5.450228 
 1927 4.037754 
 1928 4.631172 
 1929 3.605622 
 1930 3.109496 
 1931 3.689519 
 1932 4.818603 
 1933 3.745976 
 1934 4.431406 
 1935 4.937975 
 1936 3.493184 
 1937 4.321055 
 1938 4.352574 
 1939 4.760698 
 1940 5.351468 
 1941 5.975862 
 1942 4.877895 
 1943 4.310502 
 1944 5.022998 
 1945 2.147093 
 1946 5.815269 
 1947 3.765503 
 1948 4.732819 
 1949  5.09798 
 1950 3.921619 
 1951 3.077568 
 1952 5.704139 
 1953 4.577149 
 1954 4.677201 
 1955 3.886322 
 1956 4.630612 
 1957 3.097788 
 1958 5.708044 
 1959 5.256341 
 1960 5.265678 
 1961 4.608195 
 1962 4.779654 
 1963 5.551748 
 1964 3.781786 
 1965 5.093105 
 1966 6.033364 
 1967 3.885766 
 1968 3.631532 
 1969 3.274195 
 1970 5.255619 
 1971 4.271019 
 1972  3.81826 
 1973 5.206854 
 1974 3.996786 
 1975 4.348769 
 1976 5.171015 
 1977 3.499152 
 1978 4.733376 
 1979 6.076606 
 1980 5.247693 
 1981 5.507627 
 1982 5.299562 
 1983 5.038669 
 1984 3.700683 
 1985 4.473458 
 1986 5.110865 
 1987 5.933262 
 1988 5.608289 
 1989 5.488042 
 1990 5.909656 
 1991 5.396225 
 1992 5.461064 
 1993  5.84392 
 1994 5.121029 
 1995  5.46196 
 1996 4.876616 
 1997 5.662981 
 1998  5.48146 
 1999 6.840507 
 2000 5.428265 
 2001 5.925364 
 2002  6.68858 
 2003 5.606913 
 2004 6.339214 
 2005 4.913199 
 2006 5.752168 
 2007 6.668589 
 2008 4.055066 
 2009 6.740086 
 2010 5.647624 
 2011 4.958683 
 2012 3.869931 
 2013 5.189295 
 2014 5.240479 
 2015 6.215868 
 2016 6.327662 
 2017 6.760105 
 2018 5.620899