# year    value 
 1901  23.9585 
 1902 23.92409 
 1903 23.62251 
 1904  23.5786 
 1905  23.7405 
 1906 23.61227 
 1907 23.67346 
 1908 23.55118 
 1909 23.65075 
 1910 23.49506 
 1911 23.71138 
 1912 23.70476 
 1913 23.73854 
 1914 23.85851 
 1915 23.87959 
 1916 23.62073 
 1917 23.40705 
 1918 23.78408 
 1919 23.65033 
 1920 23.87265 
 1921 23.54627 
 1922 23.66468 
 1923 23.70133 
 1924  23.5343 
 1925 23.55781 
 1926 24.08111 
 1927 23.90265 
 1928 24.06565 
 1929 23.83707 
 1930 23.67211 
 1931 23.51703 
 1932 23.89697 
 1933 23.61317 
 1934 23.50249 
 1935 23.78286 
 1936 23.87276 
 1937 23.87068 
 1938  23.8809 
 1939 23.53436 
 1940 23.84221 
 1941 23.89355 
 1942 23.88114 
 1943 23.82108 
 1944 24.21788 
 1945 23.88166 
 1946 23.92954 
 1947 23.63131 
 1948 23.74517 
 1949 23.71833 
 1950 23.44922 
 1951 23.91814 
 1952 23.63568 
 1953 23.82316 
 1954 23.74464 
 1955 23.59881 
 1956 23.31007 
 1957 23.98548 
 1958 23.79064 
 1959 23.91769 
 1960 23.79756 
 1961  24.1456 
 1962 24.02093 
 1963 24.12408 
 1964 23.51139 
 1965 23.97153 
 1966 23.75988 
 1967  24.0023 
 1968 23.80374 
 1969 24.05707 
 1970 23.92946 
 1971 23.59452 
 1972 24.09793 
 1973 23.74157 
 1974 23.35922 
 1975 23.54073 
 1976 23.44626 
 1977 23.98038 
 1978 23.63697 
 1979 23.95953 
 1980  23.9384 
 1981 23.68481 
 1982 23.81754 
 1983 24.07713 
 1984 23.86755 
 1985 23.88417 
 1986 23.80353 
 1987 24.34501 
 1988 24.19537 
 1989 23.85743 
 1990   24.241 
 1991 24.08127 
 1992 23.75849 
 1993 24.02019 
 1994 24.23861 
 1995 24.39287 
 1996  24.1049 
 1997 24.56544 
 1998  24.3683 
 1999 23.96793 
 2000 24.10601 
 2001 24.07917 
 2002  24.5276 
 2003 24.40455 
 2004 24.42068 
 2005 24.47661 
 2006 24.38209 
 2007 24.46671 
 2008 24.43181 
 2009 24.58779 
 2010 24.26755 
 2011 24.17842 
 2012 24.62014 
 2013 24.48781 
 2014 24.73999 
 2015 24.88142 
 2016 24.44159 
 2017 24.53001 
 2018 24.54589