# year    value 
 1901 -12.20754 
 1902 -14.15206 
 1903 -12.7234 
 1904 -12.21889 
 1905 -12.0175 
 1906 -11.97823 
 1907 -12.58988 
 1908  -12.924 
 1909 -13.34093 
 1910 -12.92152 
 1911 -13.00156 
 1912 -12.66541 
 1913 -12.47184 
 1914 -13.31121 
 1915 -12.21186 
 1916 -13.16401 
 1917 -12.78296 
 1918 -13.2081 
 1919 -13.10837 
 1920 -11.62592 
 1921 -12.22549 
 1922 -12.52942 
 1923 -13.15839 
 1924 -11.83685 
 1925 -12.6208 
 1926 -11.82448 
 1927 -12.60822 
 1928 -12.49742 
 1929 -12.84095 
 1930 -12.40587 
 1931  -12.778 
 1932 -11.55119 
 1933 -12.90496 
 1934 -12.33126 
 1935 -12.49803 
 1936 -12.07927 
 1937 -12.20255 
 1938 -11.17121 
 1939 -11.93753 
 1940 -11.43923 
 1941 -13.06007 
 1942 -12.8004 
 1943 -10.62563 
 1944 -11.55798 
 1945 -12.1544 
 1946 -12.08655 
 1947 -11.67815 
 1948 -11.88409 
 1949 -11.71394 
 1950 -11.87275 
 1951 -12.13956 
 1952 -12.43033 
 1953 -10.69563 
 1954 -11.71127 
 1955 -13.07857 
 1956 -12.89493 
 1957 -12.46831 
 1958 -13.15254 
 1959 -12.34064 
 1960 -12.71454 
 1961 -12.7808 
 1962 -11.66372 
 1963 -13.06034 
 1964 -14.30455 
 1965 -11.80247 
 1966 -13.68838 
 1967 -11.32017 
 1968 -11.33609 
 1969 -13.30538 
 1970 -12.54056 
 1971 -12.59479 
 1972 -12.93781 
 1973 -11.93459 
 1974 -12.16777 
 1975 -11.16606 
 1976 -11.89802 
 1977 -11.60724 
 1978 -12.6798 
 1979 -12.87608 
 1980 -11.89531 
 1981 -11.58758 
 1982 -12.46052 
 1983 -12.65767 
 1984 -12.04275 
 1985 -12.5769 
 1986 -12.16527 
 1987 -12.81678 
 1988 -11.43611 
 1989 -11.52909 
 1990 -9.750965 
 1991 -11.40793 
 1992 -12.10886 
 1993 -11.1963 
 1994 -11.40415 
 1995 -10.50576 
 1996 -11.17069 
 1997 -10.67221 
 1998 -11.20408 
 1999 -11.97042 
 2000 -10.65928 
 2001 -11.65405 
 2002 -11.27733 
 2003 -10.67218 
 2004 -11.96368 
 2005 -10.37866 
 2006 -11.15562 
 2007 -10.30106 
 2008 -11.13042 
 2009 -11.62265 
 2010 -9.863169 
 2011 -9.816577 
 2012 -10.67634 
 2013 -11.43005 
 2014 -10.02222 
 2015 -10.23503 
 2016 -9.28228 
 2017 -10.20478 
 2018 -11.51088