# year    value 
 1901 4.454884 
 1902  4.15835 
 1903 4.175856 
 1904 4.581435 
 1905 4.502992 
 1906 4.187641 
 1907 4.243514 
 1908 4.145748 
 1909 4.564796 
 1910 4.199316 
 1911 4.313426 
 1912  3.24152 
 1913 4.447233 
 1914 4.279509 
 1915 4.283881 
 1916 4.105258 
 1917 4.542989 
 1918 4.450721 
 1919 4.254288 
 1920 3.940947 
 1921 4.328598 
 1922 4.230914 
 1923 4.479937 
 1924 4.536484 
 1925 4.867121 
 1926 4.709905 
 1927  5.13873 
 1928 4.515549 
 1929 4.578066 
 1930  4.52675 
 1931 4.676557 
 1932 5.078861 
 1933 4.796108 
 1934 4.437262 
 1935 4.401843 
 1936 4.774409 
 1937 4.755089 
 1938 4.854932 
 1939 4.684871 
 1940 4.574998 
 1941 4.529712 
 1942  4.99065 
 1943 4.866341 
 1944 4.526175 
 1945   5.1682 
 1946 4.666637 
 1947 4.802601 
 1948 4.525952 
 1949  4.73712 
 1950 3.997233 
 1951 4.778845 
 1952 4.162026 
 1953 4.670868 
 1954 4.927061 
 1955 4.673275 
 1956 4.214542 
 1957 4.525244 
 1958 4.735053 
 1959 4.391009 
 1960 4.528779 
 1961 4.357287 
 1962 4.483655 
 1963 5.188676 
 1964 4.318967 
 1965 4.484933 
 1966 4.545811 
 1967 4.430374 
 1968  4.34785 
 1969 4.393529 
 1970 4.262831 
 1971 4.804915 
 1972 3.953211 
 1973 4.643061 
 1974 4.329509 
 1975  4.73686 
 1976 4.026012 
 1977 4.937704 
 1978 4.710663 
 1979 4.788419 
 1980 5.067931 
 1981 4.235834 
 1982 4.442753 
 1983 5.316342 
 1984 4.215272 
 1985 4.111038 
 1986  4.41213 
 1987 4.582621 
 1988 5.428497 
 1989 4.998746 
 1990 5.594172 
 1991 4.970771 
 1992 4.386634 
 1993 4.328436 
 1994 5.214836 
 1995 5.492651 
 1996 4.333368 
 1997 4.786417 
 1998 5.434743 
 1999 5.383452 
 2000 4.313793 
 2001 5.668272 
 2002 4.979649 
 2003 5.167684 
 2004 5.376873 
 2005 5.677508 
 2006  5.52518 
 2007 5.477854 
 2008  5.60953 
 2009 5.060315 
 2010 5.718078 
 2011 5.328824 
 2012  5.34894 
 2013 5.590175 
 2014 5.627853 
 2015 5.527125 
 2016 5.166844 
 2017 5.508242 
 2018 5.451506