# year    value 
 1901 23.14162 
 1902 23.46931 
 1903 22.92388 
 1904 23.02082 
 1905 22.90199 
 1906 23.53638 
 1907 22.79016 
 1908 23.00823 
 1909 22.93863 
 1910 22.57715 
 1911 22.77781 
 1912 23.34502 
 1913 23.21799 
 1914 23.00889 
 1915 23.27822 
 1916 23.17261 
 1917 22.64852 
 1918 22.85506 
 1919 23.63049 
 1920 23.35512 
 1921 23.07765 
 1922 22.83576 
 1923 22.83725 
 1924   22.854 
 1925 23.05349 
 1926 23.23432 
 1927 23.00305 
 1928 22.95366 
 1929  22.9855 
 1930 23.17223 
 1931 22.72373 
 1932 22.88774 
 1933 23.07343 
 1934 22.69424 
 1935  23.3305 
 1936 23.23144 
 1937 22.98188 
 1938 22.72463 
 1939 22.84459 
 1940 23.29758 
 1941 23.05423 
 1942 22.90326 
 1943 23.10429 
 1944 23.04109 
 1945 23.35048 
 1946 23.09068 
 1947 23.09953 
 1948 22.78582 
 1949 22.88588 
 1950 22.86119 
 1951 22.70906 
 1952 23.25159 
 1953  23.0434 
 1954 22.67381 
 1955 22.31535 
 1956 22.07349 
 1957 23.20867 
 1958 22.89267 
 1959 22.54352 
 1960 22.65351 
 1961 23.38902 
 1962  23.0736 
 1963  23.2328 
 1964 23.06396 
 1965 22.91112 
 1966  23.3996 
 1967 23.61451 
 1968 22.42869 
 1969 23.98199 
 1970 23.61392 
 1971 22.53791 
 1972 23.20546 
 1973 23.28016 
 1974 22.77907 
 1975  22.8918 
 1976 22.25759 
 1977 22.84818 
 1978  22.9776 
 1979 22.79006 
 1980 23.59919 
 1981 23.45216 
 1982 23.13733 
 1983 23.60514 
 1984 22.96785 
 1985 23.27367 
 1986 23.12381 
 1987 23.12074 
 1988 22.95721 
 1989 22.74403 
 1990 22.98709 
 1991  23.7084 
 1992 23.60214 
 1993 23.39728 
 1994 23.65552 
 1995   23.178 
 1996 23.29111 
 1997 23.62577 
 1998 23.62992 
 1999 22.66386 
 2000 23.02594 
 2001 23.02967 
 2002 23.45486 
 2003 23.34604 
 2004 23.27959 
 2005 23.28471 
 2006 23.14785 
 2007 22.80898 
 2008 22.83039 
 2009 23.82837 
 2010 23.52313 
 2011 23.16948 
 2012 23.44144 
 2013 23.30047 
 2014 23.23384 
 2015 23.97373 
 2016 23.28794 
 2017 23.50423 
 2018 23.81908