# year    value 
 1901 13.65668 
 1902 13.33083 
 1903 13.43209 
 1904 13.59564 
 1905 13.72375 
 1906 13.54998 
 1907  13.4616 
 1908 13.45167 
 1909 13.74907 
 1910 13.37732 
 1911 13.58657 
 1912 13.17769 
 1913 13.63668 
 1914 13.58567 
 1915  13.6151 
 1916 13.47739 
 1917 13.48628 
 1918 13.68282 
 1919 13.52941 
 1920 13.47147 
 1921 13.56021 
 1922 13.56813 
 1923 13.90786 
 1924 13.76506 
 1925 13.75176 
 1926 13.89603 
 1927 14.00524 
 1928 13.85878 
 1929 13.78083 
 1930  13.8077 
 1931 13.97048 
 1932 13.85861 
 1933    13.68 
 1934  13.8531 
 1935 13.65464 
 1936 13.86394 
 1937 14.07226 
 1938 14.20217 
 1939 13.72976 
 1940 13.86647 
 1941 13.73268 
 1942 13.96594 
 1943 14.01337 
 1944 14.03686 
 1945 13.87834 
 1946 13.77714 
 1947 14.05847 
 1948  13.9258 
 1949 13.81397 
 1950  13.3769 
 1951 13.89763 
 1952 13.49469 
 1953 13.80153 
 1954 13.97807 
 1955 13.67201 
 1956 13.25812 
 1957 13.80634 
 1958 13.72523 
 1959 13.58514 
 1960 13.67721 
 1961 13.70404 
 1962 13.87055 
 1963 14.19123 
 1964 13.43455 
 1965 13.61098 
 1966 13.63352 
 1967 13.87389 
 1968 13.54872 
 1969 13.81616 
 1970  13.6652 
 1971 13.79864 
 1972 13.48834 
 1973 13.72626 
 1974 13.39249 
 1975 13.63928 
 1976 13.24352 
 1977 13.89639 
 1978 13.75406 
 1979 13.92075 
 1980 13.98417 
 1981 13.89864 
 1982 13.66589 
 1983 14.23987 
 1984  13.6186 
 1985 13.71829 
 1986 13.67078 
 1987 13.95323 
 1988 14.10845 
 1989 13.91624 
 1990 14.20298 
 1991 14.10291 
 1992 13.48385 
 1993 13.64457 
 1994 14.28322 
 1995 14.38017 
 1996 13.86192 
 1997 14.31232 
 1998 14.31646 
 1999 14.27794 
 2000 13.91762 
 2001 14.46926 
 2002 14.39806 
 2003 14.53301 
 2004 14.57262 
 2005 14.87767 
 2006 14.56325 
 2007 14.63273 
 2008  14.6464 
 2009 14.60053 
 2010 14.79669 
 2011 14.52351 
 2012 14.66738 
 2013 14.65451 
 2014 14.55691 
 2015 14.86737 
 2016 14.63947 
 2017 14.69598 
 2018 14.59833