# year    value 
 1960 9.122822 
 1961 9.833227 
 1962 8.343054 
 1963 8.339781 
 1964 8.984074 
 1965 8.349725 
 1966 9.328059 
 1967  9.27022 
 1968 8.911835 
 1969 8.619937 
 1970 8.684863 
 1971 8.970101 
 1972 8.815615 
 1973 8.833189 
 1974 9.288659 
 1975 9.289157 
 1976 8.959053 
 1977 9.271559 
 1978 8.380254 
 1979 9.038687 
 1980  8.32322 
 1981 9.007417 
 1982 9.594285 
 1983   9.5643 
 1984 8.679396 
 1985 8.665015 
 1986 9.007035 
 1987 8.868663 
 1988 9.637389 
 1989 9.775476 
 1990 9.959314 
 1991 9.062543 
 1992 9.935934 
 1993 9.446284 
 1994  10.6094 
 1995 9.569998 
 1996 8.823737 
 1997 9.852256 
 1998  9.81588 
 1999 9.895266 
 2000 10.55337 
 2001 9.841018 
 2002 10.41689 
 2003 10.14864 
 2004 9.656005 
 2005   9.3314 
 2006 10.10804 
 2007 10.47324 
 2008 10.21515 
 2009 10.27702 
 2010 9.274248 
 2011 10.61954 
 2012 10.31336 
 2013 9.938776 
 2014 11.03365 
 2015 10.89453 
 2016 10.45803 
 2017 10.46724 
 2018 11.21693