# year    value 
 1901 24.06782 
 1902 24.14531 
 1903 23.99227 
 1904 23.78368 
 1905 23.99326 
 1906 24.09231 
 1907 23.83177 
 1908 23.85465 
 1909 23.87795 
 1910 23.90032 
 1911 23.83271 
 1912 24.05805 
 1913 23.84567 
 1914  24.1322 
 1915 24.18126 
 1916 23.88789 
 1917 23.55071 
 1918 23.71102 
 1919 24.01713 
 1920 23.87088 
 1921 23.83648 
 1922 23.89695 
 1923 23.89882 
 1924 23.80695 
 1925 23.77175 
 1926 24.16343 
 1927 23.91405 
 1928 24.09834 
 1929 23.79057 
 1930 23.93473 
 1931 23.98742 
 1932  24.0144 
 1933 23.90746 
 1934 23.89604 
 1935 23.90478 
 1936 24.04108 
 1937  24.0013 
 1938 24.10504 
 1939 23.89963 
 1940 24.11182 
 1941 24.13965 
 1942 24.21279 
 1943 23.91682 
 1944 24.16195 
 1945 24.08568 
 1946 23.98317 
 1947 24.02867 
 1948 23.99123 
 1949 23.89139 
 1950 23.78924 
 1951 23.85797 
 1952 23.99876 
 1953 23.95509 
 1954 23.90345 
 1955 23.80747 
 1956 23.55397 
 1957 24.05728 
 1958 24.25988 
 1959 24.17642 
 1960 23.87101 
 1961 24.16954 
 1962 24.02118 
 1963 24.07975 
 1964 23.95709 
 1965 24.08052 
 1966 24.07607 
 1967 24.00255 
 1968 23.85507 
 1969 24.32217 
 1970 24.23963 
 1971 23.80056 
 1972 24.13066 
 1973  24.2665 
 1974 23.56989 
 1975 23.76393 
 1976 23.58675 
 1977 24.05403 
 1978 23.92639 
 1979 24.12302 
 1980  24.2539 
 1981 24.03461 
 1982 24.08578 
 1983 24.41397 
 1984 24.03242 
 1985 24.14679 
 1986 24.22494 
 1987 24.49551 
 1988 24.41666 
 1989   24.033 
 1990 24.35467 
 1991 24.34932 
 1992 24.30161 
 1993 24.31479 
 1994 24.32016 
 1995 24.45523 
 1996 24.33776 
 1997 24.42645 
 1998 24.81779 
 1999 24.29884 
 2000 24.16342 
 2001 24.35056 
 2002 24.65941 
 2003 24.64158 
 2004 24.53717 
 2005 24.83402 
 2006 24.47133 
 2007 24.50292 
 2008 24.37502 
 2009 24.60979 
 2010 24.61429 
 2011 24.29043 
 2012 24.46247 
 2013 24.68098 
 2014  24.7014 
 2015 24.85717 
 2016 24.87516 
 2017 24.79009 
 2018 24.66886