# year    value 
 1901 -8.992411 
 1902 -10.20278 
 1903 -8.91444 
 1904 -8.701885 
 1905 -8.95996 
 1906 -8.818817 
 1907 -8.896536 
 1908 -8.988558 
 1909 -8.775663 
 1910 -9.319286 
 1911 -8.60115 
 1912 -9.413684 
 1913 -9.233519 
 1914 -8.987049 
 1915 -9.423699 
 1916 -8.66755 
 1917 -9.218606 
 1918 -8.875036 
 1919 -8.903702 
 1920 -9.345202 
 1921 -8.635084 
 1922 -9.054455 
 1923 -7.938571 
 1924 -7.906781 
 1925 -8.473393 
 1926 -8.286672 
 1927 -8.604623 
 1928 -8.34793 
 1929 -8.098971 
 1930 -8.295032 
 1931 -7.496884 
 1932 -8.62592 
 1933 -9.006077 
 1934 -7.958519 
 1935 -8.943352 
 1936 -8.446668 
 1937 -7.697676 
 1938 -7.357365 
 1939 -8.531626 
 1940 -8.459186 
 1941 -8.876826 
 1942 -8.412308 
 1943 -7.158772 
 1944 -7.742495 
 1945 -8.469659 
 1946 -8.95156 
 1947 -7.393398 
 1948 -7.273065 
 1949 -8.236896 
 1950 -8.792216 
 1951 -7.836104 
 1952 -9.11861 
 1953 -8.322414 
 1954 -7.847771 
 1955 -8.743173 
 1956 -9.853914 
 1957 -9.168952 
 1958 -9.088798 
 1959 -8.452418 
 1960 -9.308616 
 1961 -8.829176 
 1962 -8.543691 
 1963 -8.470338 
 1964 -9.091153 
 1965 -9.446027 
 1966 -9.363463 
 1967 -7.590323 
 1968 -9.784599 
 1969 -8.614833 
 1970 -8.707459 
 1971 -8.337199 
 1972 -9.979915 
 1973 -8.570508 
 1974 -9.765379 
 1975 -8.767935 
 1976 -9.117343 
 1977 -8.880401 
 1978 -8.730419 
 1979 -8.860435 
 1980 -8.81231 
 1981 -7.616267 
 1982 -9.85472 
 1983 -7.947866 
 1984 -9.328282 
 1985 -8.267616 
 1986 -8.761891 
 1987 -9.04108 
 1988 -8.264339 
 1989 -9.039445 
 1990 -9.588303 
 1991 -7.865767 
 1992  -9.9037 
 1993 -8.913502 
 1994  -8.2084 
 1995 -7.690615 
 1996 -8.190745 
 1997 -7.822884 
 1998 -8.742164 
 1999 -8.051692 
 2000 -8.290534 
 2001 -7.64586 
 2002 -7.750182 
 2003 -7.211039 
 2004 -7.770074 
 2005 -6.384283 
 2006 -7.673751 
 2007 -7.046104 
 2008 -7.104589 
 2009 -7.407794 
 2010 -6.707886 
 2011 -6.998038 
 2012  -7.2812 
 2013 -7.254947 
 2014 -7.856495 
 2015 -7.416993 
 2016 -7.053965 
 2017 -7.359811 
 2018 -7.15012