# year    value 
 1901 16.14994 
 1902 16.28392 
 1903 16.13641 
 1904 16.07559 
 1905 16.19429 
 1906  15.8428 
 1907 15.60906 
 1908 16.11725 
 1909 15.94654 
 1910 15.92201 
 1911 15.47701 
 1912 15.71902 
 1913 16.01772 
 1914 16.25093 
 1915 16.04706 
 1916 15.41601 
 1917 15.56494 
 1918 15.82441 
 1919 15.81261 
 1920 15.53919 
 1921 15.51833 
 1922  15.9663 
 1923 15.86903 
 1924 15.91795 
 1925 15.98498 
 1926 16.24105 
 1927 15.83046 
 1928 15.95414 
 1929 15.84922 
 1930 16.02195 
 1931  15.9609 
 1932 16.07876 
 1933 15.89125 
 1934 16.20895 
 1935 15.91813 
 1936  15.9883 
 1937 16.18145 
 1938 16.00103 
 1939 16.30021 
 1940 16.42883 
 1941 16.34721 
 1942 15.99101 
 1943 16.00713 
 1944 16.54215 
 1945 16.22702 
 1946 15.90787 
 1947 15.95726 
 1948 16.21053 
 1949 16.01833 
 1950 16.00049 
 1951 15.97838 
 1952 15.92342 
 1953 15.93314 
 1954 15.77193 
 1955 15.74008 
 1956 15.56305 
 1957  16.0406 
 1958 16.23606 
 1959 16.23907 
 1960 16.06779 
 1961 16.27917 
 1962 15.78046 
 1963 16.19132 
 1964 15.54777 
 1965 16.27498 
 1966 16.21215 
 1967 15.90506 
 1968 15.95051 
 1969 16.40178 
 1970 16.20816 
 1971     15.9 
 1972 16.40495 
 1973 16.13095 
 1974 15.86649 
 1975  15.8725 
 1976 15.88614 
 1977 16.29874 
 1978 16.10874 
 1979 16.20061 
 1980 16.18922 
 1981 15.87625 
 1982 16.38538 
 1983 16.55652 
 1984 16.14391 
 1985 16.11953 
 1986  16.3185 
 1987 16.68739 
 1988 16.21934 
 1989 16.26586 
 1990 16.18204 
 1991 16.42116 
 1992 16.31161 
 1993 16.52226 
 1994 16.42318 
 1995 16.70365 
 1996 16.10965 
 1997 16.81863 
 1998 16.95367 
 1999  16.3501 
 2000 16.30738 
 2001 16.51075 
 2002 16.67057 
 2003 16.47985 
 2004 16.43307 
 2005  16.8419 
 2006 16.81989 
 2007 16.18843 
 2008 16.56144 
 2009 16.63365 
 2010 16.50338 
 2011 16.53851 
 2012 16.66556 
 2013  16.4677 
 2014 16.88171 
 2015 17.10949 
 2016 16.77615 
 2017  16.9866 
 2018 16.46544