# year value 1901 5.090891 1902 4.153419 1903 4.542462 1904 5.037777 1905 4.478515 1906 4.305761 1907 4.421526 1908 4.653131 1909 4.757441 1910 4.769349 1911 4.736151 1912 5.026331 1913 5.328901 1914 5.033478 1915 5.001372 1916 4.560709 1917 5.067953 1918 4.775564 1919 5.07084 1920 5.106386 1921 4.510308 1922 4.625738 1923 4.388299 1924 4.742482 1925 4.633591 1926 4.977959 1927 4.877155 1928 4.967217 1929 5.037024 1930 4.79432 1931 4.599346 1932 4.848414 1933 4.855934 1934 5.139918 1935 4.961167 1936 5.003922 1937 4.723938 1938 4.739897 1939 5.293789 1940 5.413667 1941 5.432835 1942 4.629125 1943 4.416901 1944 4.977007 1945 5.164721 1946 4.924237 1947 5.11891 1948 4.659819 1949 5.049094 1950 5.324933 1951 5.276729 1952 4.959154 1953 4.901212 1954 4.845559 1955 4.319881 1956 5.125926 1957 4.771559 1958 5.286768 1959 5.108597 1960 4.849379 1961 4.846625 1962 5.277316 1963 5.008411 1964 4.568497 1965 5.046325 1966 4.896149 1967 4.583575 1968 5.389848 1969 5.193098 1970 4.95538 1971 4.885162 1972 4.617547 1973 5.017759 1974 4.941463 1975 5.068312 1976 4.609911 1977 5.075985 1978 5.073413 1979 5.61324 1980 5.280397 1981 5.212773 1982 4.569261 1983 4.703569 1984 4.21106 1985 5.713415 1986 5.370705 1987 5.57069 1988 5.104682 1989 5.305988 1990 5.59302 1991 4.873299 1992 4.606418 1993 5.509418 1994 5.296753 1995 4.502332 1996 5.038299 1997 5.45086 1998 6.152185 1999 5.404658 2000 5.058103 2001 5.221506 2002 4.983399 2003 5.562176 2004 5.610023 2005 5.348547 2006 5.583098 2007 4.641122 2008 5.445816 2009 5.755601 2010 5.169013 2011 5.118191 2012 5.248381 2013 5.775723 2014 5.903775 2015 5.676947 2016 5.913305 2017 5.762043 2018 5.191576