# year    value 
 1979 9.433967 
 1980 8.787673 
 1981 9.493213 
 1982 9.985664 
 1983 9.956028 
 1984 9.077627 
 1985 9.114232 
 1986 9.422711 
 1987 9.393209 
 1988 10.09399 
 1989 10.16788 
 1990 10.27944 
 1991 9.325745 
 1992 10.26133 
 1993 9.809682 
 1994 11.06325 
 1995 9.991667 
 1996 9.221297 
 1997 10.26991 
 1998 10.18424 
 1999 10.28072 
 2000 10.97018 
 2001 10.36717 
 2002 10.87147 
 2003 10.78891 
 2004 10.17909 
 2005 9.816575 
 2006 10.60056 
 2007 11.01182 
 2008 10.74938 
 2009 10.79135 
 2010 9.797061 
 2011  11.0379 
 2012 10.79382 
 2013 10.42899 
 2014 11.51276 
 2015 11.38842 
 2016  10.9456 
 2017 10.97064 
 2018 11.65578