# year    value 
 1901 14.29672 
 1902 13.66454 
 1903 13.59084 
 1904 13.34705 
 1905 12.91721 
 1906 13.44132 
 1907 13.29871 
 1908 13.33733 
 1909 13.30037 
 1910 13.73598 
 1911 13.45551 
 1912 13.70386 
 1913 13.90703 
 1914 13.78159 
 1915 13.85489 
 1916 13.88949 
 1917 13.72081 
 1918 13.51925 
 1919 13.55031 
 1920  13.7853 
 1921 13.77062 
 1922 13.81268 
 1923 13.16762 
 1924 13.38575 
 1925 13.42666 
 1926 13.66565 
 1927 13.85739 
 1928 13.89831 
 1929 13.50247 
 1930 13.68217 
 1931 13.16214 
 1932 13.77025 
 1933 13.71963 
 1934 13.24932 
 1935  13.0737 
 1936 13.49461 
 1937 13.70186 
 1938 13.98502 
 1939 13.14364 
 1940 13.50818 
 1941 13.32187 
 1942 13.88629 
 1943 13.43855 
 1944 14.43566 
 1945 13.98166 
 1946 13.54707 
 1947 13.71392 
 1948 13.60359 
 1949 13.61285 
 1950 13.07857 
 1951 13.67468 
 1952 13.58281 
 1953 13.51055 
 1954 13.56619 
 1955 13.50089 
 1956 13.30311 
 1957 13.63566 
 1958 13.76123 
 1959 13.86243 
 1960 13.67467 
 1961 14.20374 
 1962 14.12886 
 1963 13.41774 
 1964  13.2923 
 1965 14.10111 
 1966 13.49265 
 1967 14.15393 
 1968 13.72738 
 1969 13.58749 
 1970 13.67554 
 1971  13.9168 
 1972  13.8674 
 1973 13.69924 
 1974 13.32935 
 1975 13.73171 
 1976 13.29092 
 1977 14.36086 
 1978 13.80064 
 1979 13.58639 
 1980 14.24856 
 1981 13.94717 
 1982 14.13996 
 1983 14.17749 
 1984  13.9157 
 1985 14.20248 
 1986 13.73921 
 1987 14.14413 
 1988 14.20541 
 1989 14.11033 
 1990 14.30678 
 1991 14.04914 
 1992 13.30011 
 1993 13.91165 
 1994 14.11029 
 1995 14.08734 
 1996 14.19446 
 1997 14.12821 
 1998 14.13145 
 1999 14.43387 
 2000 13.85648 
 2001 13.92106 
 2002 14.32583 
 2003 14.17909 
 2004  14.3026 
 2005 14.14904 
 2006 14.75082 
 2007 14.50336 
 2008 14.62067 
 2009 14.16846 
 2010 14.06841 
 2011 14.60225 
 2012 14.74638 
 2013 14.50046 
 2014 15.03496 
 2015 14.22763 
 2016 14.21913 
 2017 14.65416 
 2018 14.49213