# year value 1901 14.04684 1902 13.73611 1903 13.52551 1904 13.68262 1905 13.39447 1906 13.75592 1907 13.45122 1908 13.58969 1909 13.43661 1910 13.72436 1911 13.49478 1912 13.92509 1913 14.06929 1914 14.06864 1915 13.88241 1916 13.80506 1917 13.75869 1918 13.77716 1919 14.09769 1920 13.88466 1921 13.8651 1922 13.75717 1923 13.63752 1924 13.42013 1925 13.58957 1926 13.83559 1927 13.79922 1928 13.71186 1929 13.71287 1930 13.99083 1931 13.41208 1932 13.89874 1933 13.729 1934 13.74869 1935 13.6617 1936 13.67777 1937 13.72412 1938 13.85534 1939 13.77356 1940 13.82987 1941 13.63821 1942 13.79749 1943 13.71454 1944 14.03323 1945 14.10216 1946 13.62946 1947 13.8753 1948 13.67377 1949 13.72607 1950 13.82607 1951 13.94491 1952 13.87551 1953 13.92172 1954 13.77124 1955 13.57086 1956 13.47425 1957 13.93308 1958 13.94 1959 13.87142 1960 13.8891 1961 14.08358 1962 14.12406 1963 13.88447 1964 13.50795 1965 14.01219 1966 13.73415 1967 14.03663 1968 13.98937 1969 14.05561 1970 13.9707 1971 13.75753 1972 14.01484 1973 13.99838 1974 13.83695 1975 14.02235 1976 13.59173 1977 14.25767 1978 14.10258 1979 14.26358 1980 14.41326 1981 14.28317 1982 14.28284 1983 14.21113 1984 13.64585 1985 14.33023 1986 14.06574 1987 14.25363 1988 14.22612 1989 14.34834 1990 14.3062 1991 14.25305 1992 13.80216 1993 14.19764 1994 14.38195 1995 14.00769 1996 14.10842 1997 14.34623 1998 14.44241 1999 14.40675 2000 14.05233 2001 14.27568 2002 14.20983 2003 14.40161 2004 14.45055 2005 14.38637 2006 14.4578 2007 14.25142 2008 14.51345 2009 14.63073 2010 14.33312 2011 14.49135 2012 14.52788 2013 14.78708 2014 14.76962 2015 14.68789 2016 14.64178 2017 14.86418 2018 14.77515