# year    value 
 1980 8.842969 
 1981  8.86482 
 1982 8.838996 
 1983 9.396235 
 1984 8.414837 
 1985 8.214926 
 1986 8.264636 
 1987 8.378236 
 1988 8.939211 
 1989 8.856949 
 1990 9.370896 
 1991 9.010017 
 1992 8.395084 
 1993 7.561959 
 1994 9.687849 
 1995 9.165331 
 1996 8.372072 
 1997  8.88966 
 1998 9.209154 
 1999 9.427036 
 2000 8.583102 
 2001  9.68631 
 2002 9.028738 
 2003 9.330294 
 2004 9.858557 
 2005 10.21015 
 2006 9.618731 
 2007  9.56693 
 2008 9.733137 
 2009 9.575927 
 2010 9.924667 
 2011 9.596074 
 2012 9.622538 
 2013 9.838007 
 2014 9.092683 
 2015 9.842275 
 2016  9.44607 
 2017 9.702515 
 2018 9.238229