# year    value 
 1901 12.49185 
 1902 12.37175 
 1903 12.01591 
 1904 12.00081 
 1905 12.04668 
 1906 12.20823 
 1907 11.81452 
 1908 11.97333 
 1909 11.83539 
 1910 11.68549 
 1911 11.75479 
 1912 12.32074 
 1913 12.48849 
 1914  12.2436 
 1915 12.44262 
 1916 11.87607 
 1917 11.77966 
 1918  12.0855 
 1919 12.51864 
 1920 12.23516 
 1921 11.75555 
 1922 12.05881 
 1923 12.15452 
 1924 12.16781 
 1925 12.39548 
 1926 12.75557 
 1927 12.42834 
 1928 12.24739 
 1929 12.49082 
 1930   12.465 
 1931 12.06464 
 1932 12.46641 
 1933 12.25261 
 1934 12.13437 
 1935 12.39929 
 1936 12.38185 
 1937 12.47276 
 1938 12.22006 
 1939 12.51234 
 1940 12.50944 
 1941 12.61981 
 1942 12.24871 
 1943 12.72002 
 1944 12.93753 
 1945 12.90875 
 1946 12.45148 
 1947 12.21335 
 1948 12.25515 
 1949 11.96246 
 1950 11.86069 
 1951 12.17454 
 1952 12.04905 
 1953 12.39907 
 1954  11.8396 
 1955 11.71594 
 1956 11.40835 
 1957 12.28239 
 1958  12.3317 
 1959 12.05238 
 1960 12.08434 
 1961 12.49482 
 1962  12.1445 
 1963 12.31089 
 1964 11.98623 
 1965 12.50445 
 1966 12.22477 
 1967 12.24515 
 1968 12.19624 
 1969 12.93891 
 1970 12.46332 
 1971 11.96886 
 1972 12.59938 
 1973 12.20659 
 1974 11.76592 
 1975 11.86141 
 1976  11.9295 
 1977 12.36125 
 1978 12.23165 
 1979 12.16848 
 1980 12.47544 
 1981 12.17402 
 1982 12.49429 
 1983 12.81202 
 1984 11.99265 
 1985 12.26271 
 1986 12.44686 
 1987 12.87091 
 1988 12.28038 
 1989 12.33681 
 1990 12.29292 
 1991 12.52722 
 1992 12.47557 
 1993 12.57093 
 1994 12.90604 
 1995 12.63332 
 1996 12.14049 
 1997 13.01664 
 1998 12.85865 
 1999 12.05678 
 2000 12.11215 
 2001 12.25855 
 2002 12.41925 
 2003 12.54232 
 2004 12.56316 
 2005 12.28051 
 2006 12.70534 
 2007 11.90881 
 2008 12.31075 
 2009 12.64925 
 2010 12.39175 
 2011  12.3199 
 2012 12.69368 
 2013 12.37139 
 2014 12.67208 
 2015 12.99646 
 2016 12.76538 
 2017 12.83521 
 2018 12.44743