# year    value 
 1901 12.50922 
 1902 12.97547 
 1903 11.92913 
 1904 12.11143 
 1905  11.9704 
 1906 12.97101 
 1907 11.79753 
 1908 12.09359 
 1909 12.01651 
 1910 11.47093 
 1911 11.61201 
 1912 12.69298 
 1913 12.51326 
 1914 12.19647 
 1915 12.76413 
 1916 12.54951 
 1917  11.8752 
 1918 11.85719 
 1919 13.11529 
 1920 12.69946 
 1921 12.36434 
 1922  12.2179 
 1923 12.32912 
 1924 12.32522 
 1925 12.56229 
 1926 12.73287 
 1927 12.37254 
 1928 12.45922 
 1929 12.46784 
 1930 12.56036 
 1931 11.91342 
 1932 12.32031 
 1933 12.51837 
 1934 12.16305 
 1935 12.79157 
 1936 12.59832 
 1937 12.30436 
 1938 11.98032 
 1939 12.28794 
 1940 12.57088 
 1941 12.39609 
 1942  12.1046 
 1943 12.68432 
 1944 12.54838 
 1945 12.89347 
 1946 12.57735 
 1947 12.48265 
 1948 12.06384 
 1949 12.30556 
 1950 11.89873 
 1951  12.0254 
 1952 12.62012 
 1953  12.4429 
 1954 11.69798 
 1955 11.58112 
 1956 11.35211 
 1957 12.74068 
 1958 12.34029 
 1959 11.81823 
 1960 11.85577 
 1961 12.46701 
 1962 12.22913 
 1963 12.49513 
 1964 12.10548 
 1965 12.30696 
 1966 12.40554 
 1967 12.93784 
 1968 11.50059 
 1969 13.39419 
 1970 12.82576 
 1971 11.71454 
 1972 12.43805 
 1973 12.55842 
 1974 12.01554 
 1975  12.0049 
 1976 11.59087 
 1977 12.34484 
 1978 12.30152 
 1979 11.99255 
 1980 12.95786 
 1981 12.71758 
 1982 12.41222 
 1983 13.26193 
 1984 12.06381 
 1985 12.51035 
 1986 12.38161 
 1987 12.73703 
 1988 12.24557 
 1989 11.97251 
 1990 12.23868 
 1991 13.07714 
 1992 13.19683 
 1993 12.89915 
 1994  13.0195 
 1995  12.6384 
 1996 12.44932 
 1997 13.24112 
 1998 13.16874 
 1999 11.98858 
 2000 12.19865 
 2001 12.08021 
 2002 12.75762 
 2003 12.43535 
 2004   12.366 
 2005 12.32646 
 2006  12.5244 
 2007 11.91575 
 2008 11.88634 
 2009 13.15684 
 2010 12.75103 
 2011 12.26711 
 2012 12.77152 
 2013 12.32363 
 2014 12.32536 
 2015 13.42149 
 2016 12.61654 
 2017 12.78838 
 2018 13.00384