# year    value 
 1901  12.8239 
 1902 12.54852 
 1903 12.38616 
 1904 12.34257 
 1905 12.38877 
 1906 12.58845 
 1907 12.22217 
 1908  11.9868 
 1909 12.16231 
 1910 12.16076 
 1911 12.13255 
 1912 12.57057 
 1913 12.93998 
 1914 11.98203 
 1915 12.52837 
 1916 12.59159 
 1917 12.01394 
 1918 12.47388 
 1919  12.6088 
 1920 12.73828 
 1921  12.0736 
 1922 12.41135 
 1923 12.63836 
 1924 12.29851 
 1925 12.91635 
 1926  13.3173 
 1927 13.09292 
 1928 12.75568 
 1929 12.95455 
 1930 12.50771 
 1931 12.49111 
 1932 12.94837 
 1933 12.75327 
 1934 12.17333 
 1935 12.31996 
 1936 12.79306 
 1937 12.59194 
 1938 12.92709 
 1939 12.66029 
 1940 12.67312 
 1941  13.0805 
 1942 13.03434 
 1943 13.12543 
 1944 13.72178 
 1945 13.59903 
 1946 13.07767 
 1947 12.44945 
 1948 12.75556 
 1949 12.18732 
 1950  12.0097 
 1951 12.89087 
 1952 12.28478 
 1953 13.11727 
 1954 12.33122 
 1955    12.22 
 1956 11.94447 
 1957 12.63361 
 1958 12.58677 
 1959 12.57379 
 1960 12.43948 
 1961 12.95523 
 1962 13.12499 
 1963 12.29682 
 1964 12.42006 
 1965 12.89808 
 1966  12.7646 
 1967  12.5883 
 1968 12.89101 
 1969 13.45428 
 1970 12.99604 
 1971  12.8453 
 1972 13.00254 
 1973  12.4083 
 1974 12.20068 
 1975 12.11188 
 1976 12.49511 
 1977  12.9645 
 1978 13.00416 
 1979 12.46698 
 1980 12.45827 
 1981  12.2812 
 1982 13.09371 
 1983 12.95938 
 1984 12.90163 
 1985 12.78317 
 1986 12.84333 
 1987 13.30577 
 1988 12.90947 
 1989 12.66428 
 1990 12.91146 
 1991 12.73161 
 1992 12.57209 
 1993 12.74604 
 1994 13.48785 
 1995 13.16436 
 1996 12.69591 
 1997 13.42292 
 1998 12.70387 
 1999 12.59767 
 2000 12.56771 
 2001 12.49066 
 2002 13.14581 
 2003  13.3174 
 2004 13.30488 
 2005 12.29527 
 2006 12.94837 
 2007 12.63058 
 2008 13.07115 
 2009 13.07187 
 2010  12.5512 
 2011 13.01699 
 2012 13.37789 
 2013 12.71513 
 2014 13.53956 
 2015 13.00417 
 2016 13.01091 
 2017 12.95614 
 2018 13.25264