# year    value 
 1901 11.42173 
 1902 10.56752 
 1903 10.41338 
 1904 11.63167 
 1905 10.64881 
 1906 10.49767 
 1907 10.96052 
 1908 10.49443 
 1909 11.12057 
 1910   11.486 
 1911 9.626665 
 1912 9.965677 
 1913 10.80367 
 1914 11.64385 
 1915 10.97631 
 1916 9.749106 
 1917 11.50007 
 1918   10.689 
 1919 9.397348 
 1920 10.37504 
 1921  11.4014 
 1922 11.34159 
 1923 10.79145 
 1924 10.97973 
 1925 9.874777 
 1926 10.82121 
 1927 11.36521 
 1928  10.8778 
 1929 10.04123 
 1930 10.37063 
 1931 11.43674 
 1932 10.72527 
 1933 12.14893 
 1934 11.89419 
 1935 10.22497 
 1936 10.74422 
 1937 11.62845 
 1938 11.30903 
 1939 11.81962 
 1940 11.22546 
 1941 10.76376 
 1942 11.06926 
 1943 11.34483 
 1944 11.33418 
 1945 10.94545 
 1946 9.965568 
 1947  11.2743 
 1948 10.94468 
 1949 11.74115 
 1950 11.47124 
 1951 10.19439 
 1952 11.10653 
 1953 12.29166 
 1954 12.02822 
 1955 10.57959 
 1956 11.22745 
 1957 10.11452 
 1958 11.58528 
 1959 10.04992 
 1960  11.5586 
 1961 9.772151 
 1962 11.99299 
 1963 12.99434 
 1964 10.74953 
 1965 11.11042 
 1966 11.26918 
 1967 11.62582 
 1968 10.83378 
 1969 10.67485 
 1970 10.04187 
 1971 10.28875 
 1972  9.88557 
 1973 10.84232 
 1974 11.02706 
 1975 10.63323 
 1976 10.29281 
 1977 11.41164 
 1978 10.89479 
 1979  11.3052 
 1980 11.35856 
 1981 11.58113 
 1982 10.18552 
 1983 11.58367 
 1984 10.09911 
 1985   9.0072 
 1986 10.17572 
 1987 11.58167 
 1988 11.50565 
 1989 11.18808 
 1990 11.97028 
 1991 10.69144 
 1992 10.86072 
 1993 9.885124 
 1994 11.16421 
 1995 11.69265 
 1996 10.39548 
 1997 11.25941 
 1998 12.08078 
 1999 11.87107 
 2000 9.981431 
 2001 12.20498 
 2002 10.50561 
 2003  11.2893 
 2004 11.29421 
 2005 11.98811 
 2006 10.76773 
 2007 11.81298 
 2008 11.64499 
 2009 11.30032 
 2010 11.64322 
 2011 11.73971 
 2012 12.03433 
 2013 11.28311 
 2014  11.7989 
 2015 12.65202 
 2016 13.05122 
 2017 12.11276 
 2018 10.87987