# year    value 
 1901 7.688556 
 1902 7.326286 
 1903 6.812178 
 1904 7.950657 
 1905 7.831123 
 1906 7.192131 
 1907 7.524875 
 1908 7.417378 
 1909 6.599828 
 1910 9.978722 
 1911 7.655176 
 1912 6.407357 
 1913 7.060347 
 1914 8.710112 
 1915 7.982949 
 1916 7.973365 
 1917 5.096749 
 1918  7.40981 
 1919 8.000634 
 1920 6.404188 
 1921 7.663583 
 1922 6.257624 
 1923 7.097829 
 1924 7.276689 
 1925 9.031491 
 1926 8.950472 
 1927 7.275244 
 1928 8.622957 
 1929 7.170036 
 1930 8.084743 
 1931 8.502135 
 1932 7.507452 
 1933 6.619578 
 1934 11.01375 
 1935 6.735603 
 1936 8.867094 
 1937 7.734099 
 1938 7.599914 
 1939 8.958324 
 1940 9.306899 
 1941 8.070113 
 1942 7.153457 
 1943 8.291322 
 1944  7.00009 
 1945    6.948 
 1946 8.688677 
 1947 8.893093 
 1948 6.848916 
 1949 8.435917 
 1950 7.453191 
 1951 7.414698 
 1952 7.347773 
 1953 6.907437 
 1954 8.177894 
 1955 6.340181 
 1956 8.121776 
 1957 7.660545 
 1958 7.853034 
 1959 8.007968 
 1960 8.169355 
 1961 7.929618 
 1962 7.536418 
 1963 7.819855 
 1964 6.470032 
 1965 6.750862 
 1966 8.701201 
 1967 7.121928 
 1968 7.630198 
 1969 7.975568 
 1970 6.850861 
 1971 7.185955 
 1972 8.925421 
 1973 7.292863 
 1974 8.235668 
 1975 5.888691 
 1976 7.424192 
 1977  7.41419 
 1978 8.314367 
 1979  7.94043 
 1980 7.531713 
 1981 8.583408 
 1982 7.261358 
 1983 7.218756 
 1984 8.040033 
 1985 8.441037 
 1986 9.208495 
 1987 9.048939 
 1988 8.406953 
 1989 9.363457 
 1990 8.873096 
 1991 7.102961 
 1992 10.21511 
 1993 8.841952 
 1994 9.602945 
 1995 7.744568 
 1996 8.685993 
 1997 8.433998 
 1998 7.410634 
 1999 7.325625 
 2000 9.126102 
 2001 8.906606 
 2002 7.570121 
 2003 8.409986 
 2004 9.763954 
 2005 8.577783 
 2006 8.738653 
 2007 9.379926 
 2008 7.674598 
 2009 8.428896 
 2010 7.433463 
 2011 7.537966 
 2012 9.409396 
 2013 8.812896 
 2014 9.166613 
 2015 9.474968 
 2016 9.532142 
 2017 9.398401 
 2018 9.355001