# year    value 
 1901 24.00945 
 1902 23.68815 
 1903 23.60033 
 1904 23.52555 
 1905 23.61782 
 1906 23.76369 
 1907 23.43778 
 1908 23.42689 
 1909 23.44488 
 1910 23.65399 
 1911 23.40382 
 1912 23.73147 
 1913 23.85483 
 1914 23.30305 
 1915 23.59652 
 1916 23.81429 
 1917 23.35559 
 1918 23.58798 
 1919 23.56819 
 1920 23.78309 
 1921   23.337 
 1922 23.39414 
 1923 23.52527 
 1924 23.27915 
 1925 23.76713 
 1926   23.996 
 1927  23.7111 
 1928 23.60014 
 1929 23.75937 
 1930 23.45747 
 1931  23.4381 
 1932 23.90507 
 1933 23.65575 
 1934 23.15506 
 1935 23.40175 
 1936 23.78909 
 1937 23.68312 
 1938 23.82316 
 1939 23.58424 
 1940 23.58631 
 1941 23.85224 
 1942 24.09549 
 1943 23.97284 
 1944 24.41986 
 1945 24.29749 
 1946 23.88774 
 1947 23.63603 
 1948 23.78751 
 1949 23.44168 
 1950 23.16417 
 1951 23.80189 
 1952 23.23505 
 1953 23.86543 
 1954 23.47077 
 1955   23.575 
 1956 23.14137 
 1957 23.40183 
 1958 23.74786 
 1959 23.52635 
 1960 23.47766 
 1961 24.18022 
 1962 24.41128 
 1963 23.85262 
 1964 23.46093 
 1965 24.11742 
 1966 23.83747 
 1967 24.00583 
 1968 24.03012 
 1969 24.35577 
 1970 24.13183 
 1971 23.91992 
 1972 23.77101 
 1973 23.23027 
 1974 23.15441 
 1975 23.35613 
 1976 23.49344 
 1977 23.76688 
 1978 23.75075 
 1979 23.36725 
 1980 23.33382 
 1981 23.28144 
 1982 23.73017 
 1983 23.71062 
 1984 23.77487 
 1985 23.67746 
 1986 23.58005 
 1987 24.22394 
 1988 24.07942 
 1989  23.6411 
 1990 23.94388 
 1991  23.6451 
 1992 23.39977 
 1993 23.56656 
 1994  24.1446 
 1995  24.1379 
 1996 23.67677 
 1997 24.21978 
 1998 23.72101 
 1999 23.75982 
 2000 23.71601 
 2001 23.84632 
 2002 24.16957 
 2003 24.07376 
 2004 24.20175 
 2005 23.56546 
 2006 23.97812 
 2007 23.93052 
 2008 24.07735 
 2009 24.27212 
 2010 23.93016 
 2011 24.25779 
 2012 24.53418 
 2013 23.89237 
 2014  24.7014 
 2015 24.35985 
 2016 24.01571 
 2017 24.08247 
 2018 24.22854