# year    value 
 1901 24.97367 
 1902 24.91231 
 1903  24.5998 
 1904 24.55985 
 1905 24.69561 
 1906 24.58872 
 1907 24.66609 
 1908 24.51556 
 1909 24.65495 
 1910 24.52178 
 1911 24.72227 
 1912 24.68734 
 1913 24.69064 
 1914 24.86178 
 1915 24.89085 
 1916 24.58857 
 1917 24.41642 
 1918 24.77798 
 1919 24.62711 
 1920 24.83344 
 1921 24.53536 
 1922 24.63478 
 1923 24.63837 
 1924 24.50918 
 1925 24.48652 
 1926 25.02141 
 1927 24.84483 
 1928 25.04776 
 1929 24.79004 
 1930 24.64816 
 1931 24.45625 
 1932 24.83686 
 1933 24.56846 
 1934 24.46971 
 1935 24.76398 
 1936 24.85738 
 1937 24.86205 
 1938 24.86503 
 1939 24.46541 
 1940 24.82478 
 1941 24.83404 
 1942  24.8651 
 1943 24.77649 
 1944  25.1761 
 1945 24.79473 
 1946  24.8779 
 1947 24.59306 
 1948  24.7112 
 1949 24.69682 
 1950 24.42964 
 1951 24.88659 
 1952 24.60468 
 1953 24.76136 
 1954 24.72118 
 1955 24.59594 
 1956 24.26981 
 1957 24.95129 
 1958 24.72754 
 1959 24.90756 
 1960 24.76432 
 1961  25.1377 
 1962 25.00977 
 1963 25.12247 
 1964 24.49178 
 1965 24.96969 
 1966 24.70394 
 1967 25.00746 
 1968 24.77628 
 1969 24.99067 
 1970 24.90035 
 1971 24.57203 
 1972 25.06602 
 1973 24.70422 
 1974 24.29302 
 1975  24.5214 
 1976 24.37165 
 1977 24.92967 
 1978  24.5429 
 1979 24.94403 
 1980 24.93642 
 1981 24.65862 
 1982 24.75938 
 1983 25.05539 
 1984 24.81178 
 1985  24.8399 
 1986 24.74744 
 1987 25.31543 
 1988   25.205 
 1989 24.83257 
 1990 25.23436 
 1991 25.07463 
 1992  24.6997 
 1993 24.97619 
 1994 25.18531 
 1995 25.37078 
 1996 25.09669 
 1997 25.53544 
 1998 25.36829 
 1999 24.96582 
 2000 25.09096 
 2001 25.04551 
 2002 25.51518 
 2003 25.36356 
 2004  25.3847 
 2005 25.50207 
 2006 25.38944 
 2007  25.4723 
 2008 25.41849 
 2009 25.57265 
 2010 25.22805 
 2011 25.15794 
 2012 25.60801 
 2013 25.49944 
 2014 25.74318 
 2015 25.88139 
 2016 25.41367 
 2017  25.5172 
 2018 25.52851