# year value 1901 14.63052 1902 14.39963 1903 14.44506 1904 14.36111 1905 14.4755 1906 14.61403 1907 14.21205 1908 14.37466 1909 14.41032 1910 14.43921 1911 14.37163 1912 14.33807 1913 14.47169 1914 14.62469 1915 14.62511 1916 14.37405 1917 14.15827 1918 14.31491 1919 14.43824 1920 14.48407 1921 14.66691 1922 14.49007 1923 14.55622 1924 14.52425 1925 14.59897 1926 14.69597 1927 14.55334 1928 14.64584 1929 14.29799 1930 14.68379 1931 14.75576 1932 14.75001 1933 14.41464 1934 14.73443 1935 14.6497 1936 14.67634 1937 14.77763 1938 14.98293 1939 14.82239 1940 14.72627 1941 14.70605 1942 14.72179 1943 14.75667 1944 14.91931 1945 14.58677 1946 14.6592 1947 14.76356 1948 14.76721 1949 14.6382 1950 14.35058 1951 14.59092 1952 14.64901 1953 14.85441 1954 14.57627 1955 14.55967 1956 14.21051 1957 14.63027 1958 14.76683 1959 14.70096 1960 14.61635 1961 14.74117 1962 14.79438 1963 14.76936 1964 14.41428 1965 14.50454 1966 14.55418 1967 14.64264 1968 14.48332 1969 14.57753 1970 14.6587 1971 14.53204 1972 14.39683 1973 14.91838 1974 14.37778 1975 14.71627 1976 14.32294 1977 14.81113 1978 14.59551 1979 14.71885 1980 14.85287 1981 15.13155 1982 14.6788 1983 15.07457 1984 14.67619 1985 14.67651 1986 14.82904 1987 15.01067 1988 15.1356 1989 14.92151 1990 15.22675 1991 15.11381 1992 14.78409 1993 14.91249 1994 15.03061 1995 15.33737 1996 14.92679 1997 15.17767 1998 15.54389 1999 15.33122 2000 15.18918 2001 15.39041 2002 15.4751 2003 15.47537 2004 15.35802 2005 15.67858 2006 15.54809 2007 15.6189 2008 15.41044 2009 15.43016 2010 15.69115 2011 15.45784 2012 15.52596 2013 15.5209 2014 15.52765 2015 15.80197 2016 15.97373 2017 15.80413 2018 15.56401