# year    value 
 1940 13.82987 
 1941 13.63821 
 1942 13.79749 
 1943 13.71454 
 1944 14.03323 
 1945 14.10216 
 1946 13.62946 
 1947  13.8753 
 1948 13.67377 
 1949 13.72607 
 1950 13.82607 
 1951 13.94491 
 1952 13.87551 
 1953 13.92172 
 1954 13.77124 
 1955 13.57086 
 1956 13.47425 
 1957 13.93308 
 1958    13.94 
 1959 13.87142 
 1960  13.8891 
 1961 14.08358 
 1962 14.12406 
 1963 13.88447 
 1964 13.50795 
 1965 14.01219 
 1966 13.73415 
 1967 14.03663 
 1968 13.98937 
 1969 14.05561 
 1970  13.9707 
 1971 13.75753 
 1972 14.01484 
 1973 13.99838 
 1974 13.83695 
 1975 14.02235 
 1976 13.59173 
 1977 14.25767 
 1978 14.10258 
 1979 14.26358 
 1980 14.41326 
 1981 14.28317 
 1982 14.28284 
 1983 14.21113 
 1984 13.64585 
 1985 14.33023 
 1986 14.06574 
 1987 14.25363 
 1988 14.22612 
 1989 14.34834 
 1990  14.3062 
 1991 14.25305 
 1992 13.80216 
 1993 14.19764 
 1994 14.38195 
 1995 14.00769 
 1996 14.10842 
 1997 14.34623 
 1998 14.44241 
 1999 14.40675 
 2000 14.05233 
 2001 14.27568 
 2002 14.20983 
 2003 14.40161 
 2004 14.45055 
 2005 14.38637 
 2006  14.4578 
 2007 14.25142 
 2008 14.51345 
 2009 14.63073 
 2010 14.33312 
 2011 14.49135 
 2012 14.52788 
 2013 14.78708 
 2014 14.76962 
 2015 14.68789 
 2016 14.64178 
 2017 14.86418 
 2018 14.77515