# year    value 
 1901 16.07319 
 1902 15.53773 
 1903  15.6287 
 1904 15.78859 
 1905 15.96707 
 1906  16.0027 
 1907 15.47137 
 1908 15.91997 
 1909 15.84142 
 1910 15.92768 
 1911 15.80731 
 1912 15.43332 
 1913 15.48751 
 1914 15.91777 
 1915 15.87187 
 1916 15.83689 
 1917  15.9748 
 1918 15.82333 
 1919 15.95276 
 1920 15.86524 
 1921 16.11397 
 1922 16.19783 
 1923  16.0103 
 1924 16.18493 
 1925 15.98706 
 1926 16.14498 
 1927 16.18507 
 1928 16.09441 
 1929 15.91864 
 1930 16.20968 
 1931 16.28845 
 1932 15.98655 
 1933 16.17287 
 1934 15.99532 
 1935 16.21016 
 1936 16.04888 
 1937  16.1852 
 1938  16.1961 
 1939 16.43509 
 1940 16.11553 
 1941 16.36291 
 1942 16.20843 
 1943 16.11446 
 1944 16.33362 
 1945 16.19372 
 1946 16.39417 
 1947 16.08386 
 1948 16.33022 
 1949 16.06115 
 1950 16.25949 
 1951  16.0246 
 1952  16.2879 
 1953 16.27633 
 1954 15.99107 
 1955 16.24035 
 1956 15.78544 
 1957 15.73658 
 1958 16.13237 
 1959 16.17252 
 1960 16.12357 
 1961 16.36284 
 1962 16.06911 
 1963 16.05795 
 1964 15.88257 
 1965 15.76158 
 1966 16.11318 
 1967 15.98458 
 1968 15.77397 
 1969 15.86191 
 1970 16.26968 
 1971 16.02789 
 1972 15.70235 
 1973 16.09422 
 1974 16.05274 
 1975 16.11429 
 1976 15.43394 
 1977 16.17258 
 1978 16.03388 
 1979  16.0607 
 1980  16.2188 
 1981 16.21848 
 1982 15.97821 
 1983 15.82808 
 1984 15.93888 
 1985 16.10343 
 1986 16.27468 
 1987 15.97022 
 1988 16.40738 
 1989 16.16927 
 1990 16.45853 
 1991 16.45642 
 1992 15.84609 
 1993 15.70122 
 1994 16.86247 
 1995  16.4194 
 1996 16.35982 
 1997 16.41175 
 1998 16.91776 
 1999 16.63832 
 2000 16.93086 
 2001 16.97254 
 2002 16.94116 
 2003 16.78061 
 2004 16.59192 
 2005 16.88681 
 2006 17.08519 
 2007 17.12109 
 2008 16.99453 
 2009 16.64022 
 2010 17.11801 
 2011 17.00056 
 2012 17.17716 
 2013 17.09703 
 2014 16.91829 
 2015 17.30745 
 2016  17.3266 
 2017 17.40203 
 2018 17.44021