# year    value 
 1901 -10.39528 
 1902 -11.84027 
 1903 -10.49641 
 1904 -10.55954 
 1905 -11.03088 
 1906 -10.11711 
 1907 -10.31531 
 1908 -10.57439 
 1909 -11.00002 
 1910 -10.58086 
 1911 -10.25441 
 1912 -11.08781 
 1913 -11.06654 
 1914 -10.53091 
 1915 -11.58352 
 1916 -10.45478 
 1917 -11.17373 
 1918 -10.59064 
 1919 -10.51017 
 1920 -11.22355 
 1921 -10.13321 
 1922 -10.89505 
 1923 -9.708518 
 1924 -9.962671 
 1925 -9.52492 
 1926 -9.333428 
 1927 -10.13561 
 1928 -10.2956 
 1929 -9.998764 
 1930 -10.13427 
 1931 -9.638819 
 1932 -10.63641 
 1933 -10.16215 
 1934 -9.62659 
 1935 -10.53208 
 1936 -9.647422 
 1937 -9.03209 
 1938 -8.940742 
 1939 -10.02723 
 1940 -10.51375 
 1941 -10.65657 
 1942 -9.958591 
 1943 -8.803355 
 1944 -9.302886 
 1945 -10.06484 
 1946 -10.75841 
 1947 -8.845286 
 1948 -9.91227 
 1949 -9.582394 
 1950 -11.15361 
 1951 -9.32473 
 1952 -10.66865 
 1953 -9.807953 
 1954 -9.446177 
 1955 -11.35289 
 1956 -11.33588 
 1957 -10.26252 
 1958 -11.50124 
 1959 -9.766087 
 1960 -11.03804 
 1961 -10.72725 
 1962 -10.63192 
 1963 -10.35073 
 1964 -10.90161 
 1965 -11.15327 
 1966 -11.13683 
 1967 -9.598174 
 1968 -11.53448 
 1969 -10.60844 
 1970 -10.94482 
 1971 -10.09135 
 1972 -11.42634 
 1973 -10.62493 
 1974 -11.04114 
 1975 -10.55371 
 1976 -10.49199 
 1977 -11.28804 
 1978 -9.457204 
 1979 -10.3681 
 1980 -10.30752 
 1981 -9.577468 
 1982 -11.8495 
 1983 -10.15639 
 1984 -10.6879 
 1985 -10.40451 
 1986 -10.02913 
 1987 -10.66177 
 1988 -9.78399 
 1989 -10.79894 
 1990 -11.03372 
 1991 -9.356954 
 1992 -11.58845 
 1993 -10.30032 
 1994 -10.02101 
 1995 -8.865109 
 1996 -10.68713 
 1997 -9.553421 
 1998 -10.61328 
 1999 -10.00045 
 2000 -10.17159 
 2001 -9.705818 
 2002 -8.711553 
 2003 -8.837563 
 2004 -9.527805 
 2005 -8.309635 
 2006 -9.124116 
 2007 -8.326541 
 2008 -9.008403 
 2009 -9.299572 
 2010 -8.569134 
 2011 -9.476379 
 2012 -9.159389 
 2013 -9.114359 
 2014 -8.829357 
 2015 -8.84137 
 2016 -8.720594 
 2017 -8.989917 
 2018 -7.865912