# year    value 
 1901 -6.924739 
 1902 -5.563461 
 1903 -5.961071 
 1904 -6.925111 
 1905 -6.708731 
 1906 -6.045733 
 1907 -6.689109 
 1908 -6.196669 
 1909 -6.677866 
 1910 -5.985856 
 1911 -6.893236 
 1912 -6.405833 
 1913 -6.42316 
 1914 -4.722718 
 1915 -5.85792 
 1916 -5.651527 
 1917 -7.28424 
 1918 -7.022467 
 1919 -6.367871 
 1920 -6.659663 
 1921 -5.721989 
 1922 -6.817879 
 1923 -6.399253 
 1924 -6.21354 
 1925 -5.909384 
 1926 -5.151932 
 1927 -6.393108 
 1928 -6.64317 
 1929 -7.919904 
 1930 -6.831483 
 1931 -6.509965 
 1932 -5.349495 
 1933   -6.792 
 1934 -6.401375 
 1935 -5.69817 
 1936 -7.026453 
 1937 -6.080419 
 1938 -6.048393 
 1939 -6.132121 
 1940 -6.175234 
 1941 -5.707718 
 1942 -6.824687 
 1943 -6.32376 
 1944 -4.722288 
 1945 -7.393456 
 1946 -5.823049 
 1947 -7.275018 
 1948 -5.635452 
 1949 -5.597637 
 1950 -7.019154 
 1951 -6.84261 
 1952 -5.106904 
 1953 -5.558827 
 1954 -6.605896 
 1955 -5.410622 
 1956 -6.836032 
 1957 -6.355584 
 1958 -4.549651 
 1959 -5.914862 
 1960 -5.362981 
 1961 -5.168688 
 1962 -5.453445 
 1963 -6.010094 
 1964 -6.372241 
 1965 -6.314133 
 1966 -5.421839 
 1967 -6.912891 
 1968 -6.178212 
 1969 -7.944436 
 1970 -5.96104 
 1971 -6.251723 
 1972 -6.932592 
 1973 -5.840911 
 1974 -6.104737 
 1975 -5.096504 
 1976 -5.532907 
 1977 -6.961517 
 1978  -6.3866 
 1979 -6.691072 
 1980 -5.559919 
 1981 -4.684765 
 1982 -5.944366 
 1983 -4.088682 
 1984 -5.761785 
 1985 -7.101372 
 1986 -5.622377 
 1987 -5.008162 
 1988 -5.298141 
 1989 -4.701714 
 1990 -4.625995 
 1991 -5.175906 
 1992 -4.480747 
 1993 -5.174373 
 1994 -6.04058 
 1995 -4.161582 
 1996 -6.187071 
 1997 -5.042551 
 1998 -4.304857 
 1999 -3.75361 
 2000 -3.947585 
 2001 -5.304197 
 2002 -3.374345 
 2003 -5.810481 
 2004 -4.141999 
 2005 -5.439475 
 2006 -5.130988 
 2007 -3.403869 
 2008 -5.472262 
 2009 -5.141027 
 2010 -5.914406 
 2011 -5.812624 
 2012 -5.310179 
 2013 -5.217599 
 2014 -5.446648 
 2015 -4.21054 
 2016 -2.942053 
 2017 -4.069324 
 2018 -4.931119