# year    value 
 1901 7.945173 
 1902 7.400257 
 1903 7.700325 
 1904 8.917012 
 1905 7.928707 
 1906 7.891518 
 1907 7.209589 
 1908 7.749461 
 1909 7.723933 
 1910 7.776084 
 1911 8.034744 
 1912  8.59128 
 1913 8.652164 
 1914 8.671722 
 1915 8.179499 
 1916 8.961924 
 1917 7.205375 
 1918 8.785965 
 1919 7.089093 
 1920  10.3356 
 1921 8.841288 
 1922 8.643877 
 1923 8.570944 
 1924 8.511188 
 1925 7.716622 
 1926 8.385377 
 1927 8.991442 
 1928 7.591491 
 1929 7.528579 
 1930 8.633135 
 1931 7.647321 
 1932 6.914222 
 1933 7.957045 
 1934 9.899282 
 1935 7.098955 
 1936 9.024545 
 1937 8.752932 
 1938 7.664928 
 1939 7.348433 
 1940 7.902626 
 1941 7.079482 
 1942 8.365627 
 1943 9.565804 
 1944  7.67831 
 1945 10.12046 
 1946 10.05457 
 1947 10.07976 
 1948 10.04137 
 1949 8.516206 
 1950 9.298742 
 1951  7.94199 
 1952 9.119364 
 1953 9.198143 
 1954 7.936756 
 1955 7.230491 
 1956 7.616546 
 1957  8.45029 
 1958 7.459531 
 1959 9.552513 
 1960 8.849976 
 1961 9.709095 
 1962 7.023818 
 1963 8.211524 
 1964 8.509182 
 1965 7.546219 
 1966 8.904631 
 1967 8.608526 
 1968 8.999194 
 1969 8.417447 
 1970   6.7137 
 1971 8.234891 
 1972 8.755931 
 1973  7.66993 
 1974 8.544637 
 1975 8.453405 
 1976 7.956964 
 1977 8.723464 
 1978 7.717937 
 1979 8.362166 
 1980 7.078714 
 1981 9.411821 
 1982 8.148686 
 1983  8.93313 
 1984 7.053294 
 1985 8.276267 
 1986 8.818941 
 1987 6.885804 
 1988 8.752639 
 1989 9.798386 
 1990 9.763118 
 1991 8.102919 
 1992 9.388586 
 1993 9.319204 
 1994 9.747515 
 1995 8.459103 
 1996 8.269896 
 1997  9.10321 
 1998 9.180304 
 1999 9.907219 
 2000  10.3798 
 2001 9.951436 
 2002 9.883068 
 2003 10.05341 
 2004 8.433072 
 2005 9.050919 
 2006 8.707464 
 2007 11.03552 
 2008 9.355375 
 2009 10.47408 
 2010 8.893717 
 2011 10.74334 
 2012 10.33216 
 2013 8.482801 
 2014 10.40857 
 2015  9.87748 
 2016 9.399471 
 2017  10.5531 
 2018 10.71112