# year    value 
 1901 13.24826 
 1902 13.27221 
 1903 12.30428 
 1904 12.83141 
 1905 11.85553 
 1906 12.86805 
 1907  12.3978 
 1908 12.75928 
 1909 12.97649 
 1910 12.65704 
 1911 12.70345 
 1912 12.96613 
 1913 12.39308 
 1914  13.0143 
 1915 13.25894 
 1916 13.22691 
 1917 12.69615 
 1918 12.70483 
 1919 13.10839 
 1920 12.42762 
 1921 13.27472 
 1922 13.51048 
 1923  13.3147 
 1924 13.08739 
 1925 13.12967 
 1926 12.88621 
 1927 12.61803 
 1928 13.27757 
 1929 13.70736 
 1930 13.12741 
 1931 13.20882 
 1932 13.46375 
 1933 12.85739 
 1934 12.54185 
 1935 13.16598 
 1936 12.42713 
 1937 12.57791 
 1938 13.90247 
 1939 12.68707 
 1940 13.01144 
 1941 14.12831 
 1942 13.74279 
 1943 13.03729 
 1944 13.56588 
 1945 13.18323 
 1946 13.55002 
 1947 13.90951 
 1948 13.45632 
 1949 13.09473 
 1950 13.08622 
 1951 12.46946 
 1952  13.2031 
 1953 13.54907 
 1954 12.81711 
 1955 12.75506 
 1956  13.3028 
 1957   12.374 
 1958 13.64279 
 1959 13.30643 
 1960 12.50919 
 1961 13.58781 
 1962 13.11061 
 1963 13.30601 
 1964 13.45135 
 1965 12.85327 
 1966 13.19764 
 1967 12.98342 
 1968  12.9885 
 1969 13.42665 
 1970 12.79703 
 1971 13.16522 
 1972 13.20421 
 1973 13.62842 
 1974 13.45721 
 1975 13.21103 
 1976 12.54422 
 1977 13.55309 
 1978  13.4211 
 1979 12.90364 
 1980 13.34595 
 1981 13.79796 
 1982 13.09821 
 1983 12.84762 
 1984 13.45135 
 1985 13.22519 
 1986 13.05306 
 1987 13.22746 
 1988 13.19118 
 1989 13.15467 
 1990 13.19778 
 1991 13.12699 
 1992 13.10991 
 1993 13.07492 
 1994 13.59494 
 1995 13.33055 
 1996 13.05173 
 1997 13.76363 
 1998 13.92849 
 1999 13.90875 
 2000 14.18175 
 2001  14.1931 
 2002  14.2653 
 2003 13.40013 
 2004 14.65583 
 2005 13.97261 
 2006 14.21511 
 2007  14.4475 
 2008 14.88311 
 2009 14.39099 
 2010 14.15162 
 2011  13.8115 
 2012 14.11374 
 2013 14.43684 
 2014 13.78194 
 2015 14.18828 
 2016 14.73043 
 2017 14.27146 
 2018 14.96528