# year    value 
 1901 25.37632 
 1902 25.53206 
 1903 25.19947 
 1904 25.17777 
 1905 25.01468 
 1906 25.34194 
 1907 24.98723 
 1908 25.45404 
 1909 25.39524 
 1910  25.0713 
 1911 25.03094 
 1912 25.29514 
 1913   24.939 
 1914  25.2245 
 1915 25.24075 
 1916 25.35463 
 1917  24.8754 
 1918 24.91689 
 1919 25.36801 
 1920 25.09731 
 1921 25.37972 
 1922 25.35307 
 1923 25.25151 
 1924  25.6503 
 1925 25.40441 
 1926 25.22989 
 1927 25.22228 
 1928 25.58639 
 1929  25.4161 
 1930 25.24898 
 1931 25.56636 
 1932  25.3712 
 1933 25.39743 
 1934 25.38803 
 1935 25.60784 
 1936 25.65447 
 1937  25.5565 
 1938 25.58297 
 1939 25.42393 
 1940 25.39224 
 1941 25.85965 
 1942 25.70984 
 1943 25.12184 
 1944 25.37955 
 1945 25.23494 
 1946 25.49228 
 1947 25.58127 
 1948 25.32834 
 1949 25.37421 
 1950 25.14711 
 1951 25.31895 
 1952  25.5111 
 1953 25.50161 
 1954 25.47917 
 1955 25.41354 
 1956 25.29337 
 1957 24.98839 
 1958 26.00724 
 1959 25.53477 
 1960 25.30362 
 1961 25.43888 
 1962 25.34906 
 1963 25.18275 
 1964 25.64447 
 1965 25.03191 
 1966 25.41451 
 1967 25.07889 
 1968  24.8722 
 1969 25.92815 
 1970 25.47356 
 1971  25.2163 
 1972 25.21891 
 1973  25.8011 
 1974 25.32974 
 1975 25.41171 
 1976 24.99055 
 1977  25.4319 
 1978 25.61774 
 1979 25.60171 
 1980 25.94402 
 1981 25.63804 
 1982 25.34718 
 1983 25.59113 
 1984 25.84309 
 1985 25.60713 
 1986 25.60518 
 1987  25.6757 
 1988 26.01981 
 1989  25.4008 
 1990 25.62695 
 1991 25.80335 
 1992 25.47027 
 1993 25.52884 
 1994 25.81606 
 1995 25.74901 
 1996 25.73203 
 1997 25.45888 
 1998 26.32746 
 1999 25.96752 
 2000 25.95858 
 2001 26.20313 
 2002 26.32324 
 2003 26.23806 
 2004 26.22907 
 2005 26.27397 
 2006 26.06946 
 2007 26.24609 
 2008 26.15745 
 2009 26.20871 
 2010 26.79331 
 2011 26.10591 
 2012 26.11468 
 2013  26.3137 
 2014 26.18842 
 2015 26.19802 
 2016  26.6893 
 2017 26.27908 
 2018 26.29853