# year value 1901 5.686974 1902 6.064498 1903 5.912176 1904 5.451291 1905 5.700593 1906 5.775878 1907 5.682549 1908 5.712748 1909 5.554805 1910 5.792745 1911 5.406566 1912 5.962742 1913 5.567213 1914 6.470451 1915 5.95923 1916 5.974812 1917 5.251523 1918 5.354748 1919 5.655337 1920 5.790291 1921 5.954367 1922 5.605451 1923 5.852474 1924 5.950037 1925 5.747127 1926 6.563587 1927 5.797253 1928 5.908282 1929 5.464103 1930 5.593528 1931 5.884185 1932 6.298808 1933 5.619675 1934 5.978671 1935 6.334957 1936 5.658578 1937 6.171106 1938 6.165019 1939 6.13413 1940 6.307892 1941 6.284885 1942 5.97998 1943 6.079202 1944 6.645885 1945 5.73182 1946 6.033638 1947 5.718174 1948 6.220214 1949 5.982871 1950 5.499009 1951 5.45568 1952 6.327468 1953 6.215911 1954 5.846299 1955 6.153781 1956 5.539735 1957 5.682355 1958 6.594135 1959 6.179297 1960 6.267103 1961 6.391022 1962 6.207077 1963 6.379854 1964 5.930373 1965 5.738909 1966 5.908399 1967 5.632492 1968 5.85322 1969 5.295462 1970 6.329066 1971 5.760947 1972 5.441512 1973 6.34663 1974 5.634224 1975 5.997068 1976 5.914668 1977 5.83583 1978 6.123118 1979 5.833296 1980 6.457575 1981 6.743336 1982 6.238095 1983 6.679173 1984 6.155585 1985 5.700898 1986 6.428068 1987 6.485773 1988 6.635434 1989 6.47876 1990 6.532582 1991 6.599517 1992 6.557526 1993 6.529917 1994 6.170564 1995 6.999128 1996 6.408893 1997 6.563912 1998 6.975681 1999 7.155775 2000 6.877654 2001 6.506906 2002 7.182815 2003 6.806849 2004 7.156206 2005 6.705616 2006 6.974257 2007 7.424023 2008 6.550348 2009 6.864415 2010 6.810998 2011 6.554956 2012 6.647638 2013 6.741651 2014 6.806244 2015 7.327003 2016 7.875218 2017 7.398457 2018 7.159111