# year    value 
 1901 -10.18416 
 1902 -11.22778 
 1903 -10.1943 
 1904 -10.2649 
 1905 -10.06161 
 1906 -10.12794 
 1907 -10.62344 
 1908 -10.39272 
 1909 -10.59665 
 1910 -10.51002 
 1911 -10.38064 
 1912 -10.53657 
 1913 -10.34197 
 1914 -10.21307 
 1915 -10.55773 
 1916 -10.54073 
 1917 -10.57014 
 1918 -10.70575 
 1919 -10.69791 
 1920 -10.06066 
 1921 -9.981241 
 1922 -10.43986 
 1923 -10.03255 
 1924 -9.809927 
 1925 -10.00738 
 1926 -9.633843 
 1927 -10.12048 
 1928 -9.708403 
 1929 -10.10381 
 1930 -9.780129 
 1931 -9.786471 
 1932 -9.661785 
 1933 -10.59157 
 1934 -9.34974 
 1935 -9.830268 
 1936 -9.883113 
 1937 -9.383972 
 1938 -9.122195 
 1939 -9.57524 
 1940 -9.597842 
 1941 -10.31343 
 1942 -9.738471 
 1943 -8.842418 
 1944 -9.051498 
 1945 -9.707617 
 1946 -10.30236 
 1947 -9.519439 
 1948 -9.577353 
 1949 -9.763719 
 1950 -10.21745 
 1951 -10.02985 
 1952 -10.19755 
 1953 -9.264173 
 1954 -9.638207 
 1955 -10.50115 
 1956 -10.48015 
 1957 -10.0163 
 1958 -10.41174 
 1959 -9.714555 
 1960 -9.965798 
 1961 -10.21581 
 1962 -9.47803 
 1963 -9.850521 
 1964 -10.62671 
 1965 -10.54306 
 1966 -11.06641 
 1967 -9.518609 
 1968 -10.33789 
 1969 -10.37994 
 1970 -10.21642 
 1971 -10.15069 
 1972 -10.80745 
 1973 -9.743728 
 1974 -10.45957 
 1975 -9.64812 
 1976 -10.25055 
 1977 -9.814696 
 1978 -10.06567 
 1979 -10.58184 
 1980 -9.724076 
 1981 -8.660534 
 1982 -10.42981 
 1983 -9.620382 
 1984 -9.944258 
 1985 -9.976953 
 1986 -9.865552 
 1987 -10.31979 
 1988 -9.146951 
 1989 -9.490275 
 1990 -9.536586 
 1991 -9.22379 
 1992 -10.02528 
 1993 -9.296142 
 1994 -9.658968 
 1995 -8.56276 
 1996 -9.375507 
 1997 -9.118554 
 1998 -9.364582 
 1999 -9.567954 
 2000 -9.088093 
 2001 -9.071424 
 2002 -8.92365 
 2003 -8.448406 
 2004 -9.491355 
 2005 -8.094555 
 2006 -8.790411 
 2007 -8.210637 
 2008 -8.688286 
 2009 -9.147046 
 2010 -8.448317 
 2011 -8.175687 
 2012 -8.657322 
 2013 -8.745675 
 2014 -8.35871 
 2015 -8.323686 
 2016 -7.594721 
 2017 -8.093968 
 2018 -8.525492