# year    value 
 1901 13.04364 
 1902 12.81179 
 1903 12.83555 
 1904 12.78257 
 1905 12.86582 
 1906 12.99941 
 1907 12.63269 
 1908 12.79256 
 1909 12.78299 
 1910 12.82352 
 1911 12.76135 
 1912  12.7288 
 1913 12.84352 
 1914 13.04313 
 1915 13.01458 
 1916 12.76851 
 1917 12.60487 
 1918 12.73628 
 1919 12.83207 
 1920 12.86788 
 1921 13.05898 
 1922 12.88796 
 1923 12.96694 
 1924 12.94396 
 1925 13.02544 
 1926 13.16386 
 1927  12.9835 
 1928 13.05829 
 1929 12.72805 
 1930 13.06625 
 1931 13.11388 
 1932 13.14414 
 1933 12.82436 
 1934 13.15642 
 1935 13.04242 
 1936 13.06261 
 1937 13.15171 
 1938 13.35802 
 1939 13.24863 
 1940 13.17666 
 1941 13.15951 
 1942 13.14712 
 1943 13.20099 
 1944 13.30458 
 1945 13.03083 
 1946 13.09477 
 1947 13.18539 
 1948 13.18356 
 1949 13.04337 
 1950 12.77763 
 1951 13.00084 
 1952 13.03668 
 1953 13.28267 
 1954 12.98037 
 1955 12.95512 
 1956 12.62395 
 1957 13.01536 
 1958 13.20652 
 1959 13.12143 
 1960   13.043 
 1961 13.14822 
 1962 13.20271 
 1963 13.21376 
 1964 12.79965 
 1965 12.90082 
 1966 12.97327 
 1967 13.03524 
 1968 12.90209 
 1969 12.97499 
 1970 13.06623 
 1971 12.94189 
 1972 12.81276 
 1973 13.30269 
 1974 12.79275 
 1975  13.1117 
 1976 12.75043 
 1977  13.2134 
 1978 13.06831 
 1979 13.15167 
 1980 13.27579 
 1981 13.53112 
 1982 13.08872 
 1983 13.46417 
 1984  13.0631 
 1985 13.08781 
 1986 13.26424 
 1987   13.412 
 1988  13.5594 
 1989 13.36128 
 1990 13.64446 
 1991 13.51321 
 1992 13.21404 
 1993 13.33693 
 1994 13.49213 
 1995 13.76269 
 1996 13.33751 
 1997  13.6118 
 1998 13.95871 
 1999 13.73528 
 2000 13.59777 
 2001 13.80345 
 2002 13.90487 
 2003 13.89999 
 2004  13.7901 
 2005 14.04376 
 2006 13.95272 
 2007 14.04784 
 2008  13.8226 
 2009 13.84988 
 2010 14.07428 
 2011 13.85595 
 2012 13.89461 
 2013  13.9379 
 2014 13.98022 
 2015 14.25259 
 2016 14.38873 
 2017 14.24464 
 2018 14.03128