# year value 1901 10.31532 1902 9.820928 1903 9.300312 1904 9.992406 1905 9.603191 1906 9.890924 1907 9.816139 1908 9.871717 1909 9.543066 1910 10.62663 1911 9.603464 1912 9.084284 1913 9.456303 1914 10.21274 1915 9.777613 1916 9.201002 1917 9.309958 1918 10.02223 1919 9.546218 1920 9.565835 1921 10.72706 1922 9.682651 1923 9.823137 1924 9.454444 1925 10.42037 1926 10.47095 1927 9.909471 1928 10.22093 1929 9.37753 1930 10.0204 1931 10.87135 1932 9.663435 1933 10.47524 1934 11.79765 1935 10.05939 1936 10.42726 1937 9.877399 1938 10.63525 1939 10.85958 1940 10.64113 1941 10.4695 1942 10.04327 1943 10.37457 1944 9.86899 1945 9.922715 1946 10.4995 1947 10.20172 1948 9.736117 1949 9.758984 1950 9.844168 1951 9.446899 1952 10.15122 1953 10.8032 1954 10.87054 1955 9.625838 1956 10.2814 1957 10.07801 1958 10.71547 1959 10.22437 1960 10.05729 1961 10.25222 1962 10.26475 1963 10.70952 1964 9.785948 1965 9.894446 1966 10.07791 1967 10.26852 1968 9.910762 1969 10.04331 1970 9.986727 1971 9.832383 1972 9.855389 1973 10.1135 1974 10.37483 1975 9.533936 1976 10.16963 1977 10.68838 1978 9.808916 1979 9.689789 1980 10.62201 1981 11.21535 1982 9.555385 1983 10.19139 1984 10.05533 1985 9.555682 1986 10.92882 1987 10.92085 1988 10.71425 1989 10.18772 1990 10.7315 1991 10.55887 1992 10.75718 1993 9.659569 1994 10.94802 1995 10.79353 1996 10.364 1997 10.2441 1998 10.86348 1999 10.88502 2000 10.71172 2001 10.93129 2002 10.48467 2003 11.05212 2004 10.75209 2005 11.02122 2006 11.3957 2007 10.95 2008 10.34763 2009 10.35697 2010 10.64012 2011 10.52622 2012 11.84813 2013 10.47066 2014 11.00987 2015 11.74409 2016 11.81562 2017 11.39518 2018 11.05809