# year    value 
 1901 23.14665 
 1902 23.41994 
 1903 23.22996 
 1904 22.93535 
 1905 23.11719 
 1906 23.34656 
 1907 22.93929 
 1908 23.03124 
 1909 22.93622 
 1910 22.95739 
 1911 22.86349 
 1912 23.37766 
 1913 22.93257 
 1914 23.34427 
 1915 23.42797 
 1916 23.12052 
 1917 22.59989 
 1918 22.69389 
 1919 23.33953 
 1920 22.98697 
 1921  23.1048 
 1922 23.14822 
 1923 23.16669 
 1924 23.01692 
 1925 23.00825 
 1926 23.27718 
 1927 23.03743 
 1928 23.35211 
 1929 22.74943 
 1930 23.08664 
 1931 23.22039 
 1932 23.17146 
 1933 23.30415 
 1934 23.16515 
 1935 22.97742 
 1936 23.14173 
 1937 23.07647 
 1938 23.36324 
 1939 23.14175 
 1940 23.17807 
 1941 23.46658 
 1942 23.47834 
 1943 23.19213 
 1944 22.98441 
 1945 23.21521 
 1946 23.13812 
 1947 23.19557 
 1948 23.05549 
 1949 23.00082 
 1950 22.99148 
 1951 22.99416 
 1952 23.25104 
 1953 23.28122 
 1954 23.10807 
 1955 22.85408 
 1956  22.7676 
 1957 23.23231 
 1958 23.65564 
 1959 23.36884 
 1960 22.76527 
 1961  23.4491 
 1962 22.99812 
 1963 23.11638 
 1964 23.34977 
 1965 23.06026 
 1966 23.28903 
 1967 23.23477 
 1968 22.70989 
 1969 23.61969 
 1970 23.46353 
 1971 22.92909 
 1972 23.14666 
 1973 23.74308 
 1974   22.768 
 1975  22.9858 
 1976 22.71239 
 1977 23.07649 
 1978 23.18964 
 1979 23.17772 
 1980 23.67433 
 1981 23.38256 
 1982 23.13323 
 1983 23.82066 
 1984 23.29037 
 1985 23.40032 
 1986 23.64849 
 1987 23.72998 
 1988  23.6682 
 1989 23.21776 
 1990 23.65993 
 1991 23.62486 
 1992 23.89692 
 1993 23.72872 
 1994 23.53414 
 1995 23.46016 
 1996 23.41399 
 1997 23.30272 
 1998 24.15842 
 1999 23.45323 
 2000 23.28154 
 2001 23.53132 
 2002 24.06928 
 2003 23.79934 
 2004 23.71252 
 2005 24.13075 
 2006 23.38082 
 2007 23.77608 
 2008 23.25321 
 2009 23.69153 
 2010 24.00763 
 2011 23.33664 
 2012 23.44948 
 2013 23.75227 
 2014 23.83089 
 2015 23.78902 
 2016 24.18429 
 2017 23.91039 
 2018 23.95703