# year    value 
 1901 -9.734251 
 1902 -8.920573 
 1903 -9.235744 
 1904 -9.932933 
 1905 -9.413213 
 1906 -10.05764 
 1907 -9.406749 
 1908 -9.546971 
 1909 -10.06497 
 1910 -9.642303 
 1911 -10.08436 
 1912 -9.120704 
 1913 -10.24569 
 1914 -8.384258 
 1915 -9.89669 
 1916 -9.085507 
 1917 -10.14126 
 1918 -9.456065 
 1919 -10.28368 
 1920 -9.548819 
 1921 -9.414871 
 1922 -10.29954 
 1923 -9.743108 
 1924 -9.439311 
 1925 -9.636746 
 1926 -8.227146 
 1927 -9.75488 
 1928 -9.795501 
 1929 -11.09783 
 1930 -10.44155 
 1931 -10.2401 
 1932 -9.366667 
 1933 -10.59966 
 1934 -8.889618 
 1935 -8.693289 
 1936 -10.18386 
 1937 -9.957525 
 1938 -9.48749 
 1939 -9.334892 
 1940 -8.555778 
 1941 -8.495195 
 1942 -9.886076 
 1943 -9.177285 
 1944 -8.944537 
 1945 -10.90346 
 1946 -8.86492 
 1947 -10.28373 
 1948 -9.095758 
 1949 -9.372684 
 1950 -10.30129 
 1951 -10.10125 
 1952 -9.104816 
 1953 -9.229248 
 1954 -9.458283 
 1955 -9.703669 
 1956 -9.522196 
 1957 -10.5786 
 1958 -8.15944 
 1959 -8.752323 
 1960 -8.880212 
 1961 -8.952106 
 1962 -8.916055 
 1963 -8.16588 
 1964 -9.807961 
 1965 -9.433093 
 1966 -8.881655 
 1967 -9.586677 
 1968 -9.799956 
 1969 -11.00749 
 1970 -8.725858 
 1971 -9.406701 
 1972 -9.886993 
 1973 -9.257851 
 1974 -9.41683 
 1975 -9.487209 
 1976 -8.798359 
 1977 -9.84121 
 1978 -9.053239 
 1979 -8.886936 
 1980 -8.675076 
 1981 -8.258942 
 1982 -8.661836 
 1983 -8.65074 
 1984 -9.282032 
 1985 -9.947277 
 1986 -8.618103 
 1987 -8.225763 
 1988 -8.454613 
 1989 -8.506812 
 1990 -8.113792 
 1991 -8.413166 
 1992 -8.239788 
 1993 -8.688842 
 1994 -8.333364 
 1995 -7.859951 
 1996 -8.519842 
 1997 -8.116488 
 1998 -8.019544 
 1999 -7.275635 
 2000 -8.276635 
 2001 -8.707239 
 2002 -7.469077 
 2003 -8.212566 
 2004 -7.632097 
 2005 -9.054925 
 2006 -8.296117 
 2007 -7.352996 
 2008  -9.0444 
 2009 -8.050444 
 2010 -8.588717 
 2011 -8.751688 
 2012 -9.319829 
 2013 -8.828709 
 2014 -8.188306 
 2015 -7.075165 
 2016 -7.397095 
 2017 -7.646793 
 2018 -7.998235