# year    value 
 1901 -9.928247 
 1902 -10.95196 
 1903 -9.876263 
 1904 -9.948474 
 1905 -9.754139 
 1906 -9.861054 
 1907 -10.34538 
 1908 -10.12517 
 1909 -10.2207 
 1910 -10.20458 
 1911 -10.08885 
 1912 -10.28906 
 1913 -10.03462 
 1914 -10.02032 
 1915 -10.24595 
 1916 -10.18478 
 1917 -10.33338 
 1918 -10.44753 
 1919 -10.41498 
 1920 -9.703777 
 1921 -9.698832 
 1922 -10.12754 
 1923 -9.747622 
 1924 -9.459241 
 1925 -9.732293 
 1926 -9.495781 
 1927 -9.85347 
 1928 -9.389846 
 1929 -9.83245 
 1930 -9.465278 
 1931 -9.40103 
 1932 -9.265997 
 1933 -10.30563 
 1934  -9.0707 
 1935 -9.494694 
 1936 -9.60327 
 1937 -9.108185 
 1938 -8.808574 
 1939 -9.285751 
 1940 -9.390089 
 1941 -10.09375 
 1942 -9.486206 
 1943 -8.579862 
 1944 -8.757457 
 1945 -9.468785 
 1946 -9.932595 
 1947 -9.258878 
 1948 -9.239118 
 1949 -9.469066 
 1950 -9.88449 
 1951 -9.727489 
 1952 -9.854109 
 1953 -8.962544 
 1954 -9.288301 
 1955 -10.18659 
 1956 -10.17247 
 1957 -9.780943 
 1958 -10.13754 
 1959 -9.421978 
 1960 -9.734315 
 1961 -9.871781 
 1962 -9.208339 
 1963 -9.662924 
 1964 -10.28559 
 1965 -10.1981 
 1966 -10.76738 
 1967 -9.183441 
 1968 -10.12367 
 1969 -10.12626 
 1970 -9.960905 
 1971 -9.836416 
 1972 -10.5291 
 1973 -9.38618 
 1974 -10.14568 
 1975 -9.329671 
 1976 -9.958095 
 1977 -9.502207 
 1978 -9.950944 
 1979 -10.35303 
 1980 -9.47318 
 1981 -8.406001 
 1982 -10.13548 
 1983 -9.392008 
 1984 -9.669433 
 1985 -9.760004 
 1986 -9.701189 
 1987  -10.051 
 1988 -8.921512 
 1989 -9.254877 
 1990 -9.286614 
 1991 -9.006636 
 1992 -9.788458 
 1993 -9.068098 
 1994 -9.39524 
 1995 -8.314647 
 1996 -9.032304 
 1997 -8.93435 
 1998 -9.06886 
 1999 -9.197039 
 2000 -8.820072 
 2001 -8.777466 
 2002 -8.740242 
 2003 -8.196389 
 2004 -9.263504 
 2005 -7.797254 
 2006 -8.434976 
 2007 -7.951451 
 2008 -8.367248 
 2009 -8.877453 
 2010 -8.144529 
 2011 -7.830466 
 2012 -8.284271 
 2013 -8.476669 
 2014 -8.168446 
 2015 -8.11283 
 2016 -7.350443 
 2017 -7.869386 
 2018 -8.369155