# year value 1901 14.84057 1902 14.88013 1903 15.1214 1904 14.02356 1905 14.33311 1906 14.57868 1907 14.42507 1908 14.7779 1909 14.39821 1910 14.13929 1911 14.26724 1912 15.44861 1913 15.07641 1914 15.1412 1915 15.32767 1916 14.94807 1917 14.49801 1918 14.27873 1919 15.48006 1920 15.29926 1921 14.63489 1922 15.06989 1923 14.86095 1924 15.05735 1925 14.88064 1926 15.56177 1927 15.2848 1928 15.09757 1929 15.23808 1930 15.49558 1931 15.28131 1932 15.2579 1933 14.80494 1934 14.78377 1935 15.04843 1936 15.22813 1937 15.25334 1938 15.06582 1939 15.3751 1940 14.61954 1941 15.14934 1942 15.54883 1943 15.49657 1944 15.16404 1945 15.61212 1946 15.25958 1947 15.16507 1948 14.89777 1949 14.94143 1950 14.43425 1951 14.30215 1952 14.93786 1953 14.9698 1954 14.80831 1955 14.97877 1956 14.22783 1957 14.58158 1958 15.34827 1959 14.61903 1960 14.9704 1961 15.27337 1962 14.89585 1963 14.78834 1964 15.14978 1965 14.92806 1966 14.86599 1967 14.86454 1968 14.91738 1969 15.40524 1970 15.30519 1971 14.40872 1972 15.19221 1973 15.67635 1974 14.16844 1975 14.32911 1976 14.60148 1977 15.12289 1978 14.63274 1979 14.78218 1980 15.03792 1981 14.82369 1982 14.91624 1983 15.7609 1984 14.97363 1985 14.45808 1986 14.95255 1987 15.63315 1988 15.18199 1989 15.41331 1990 15.10116 1991 14.99383 1992 14.94631 1993 15.00513 1994 15.08967 1995 15.45681 1996 15.00292 1997 14.75275 1998 15.74973 1999 15.06435 2000 14.68213 2001 15.23848 2002 14.8382 2003 15.2704 2004 15.21245 2005 15.49205 2006 15.01748 2007 15.30369 2008 14.74189 2009 15.10145 2010 15.55697 2011 14.77403 2012 15.12665 2013 15.32218 2014 15.30523 2015 15.091 2016 16.01388 2017 15.89625 2018 15.14108