# year    value 
 1979 10.03801 
 1980 10.87267 
 1981 12.09748 
 1982 10.43173 
 1983 9.892708 
 1984 10.66954 
 1985 12.40142 
 1986 12.38026 
 1987 12.05349 
 1988 11.77404 
 1989 11.62298 
 1990 11.33872 
 1991 11.81034 
 1992 12.34886 
 1993 11.10283 
 1994 12.11547 
 1995 10.09084 
 1996  10.3844 
 1997 10.33989 
 1998 10.89621 
 1999 10.97588 
 2000 12.44884 
 2001 11.48721 
 2002 9.949688 
 2003 11.44591 
 2004 12.46504 
 2005 11.62153 
 2006 12.64734 
 2007 12.26854 
 2008 10.93168 
 2009  11.0842 
 2010 11.56308 
 2011 11.02529 
 2012 13.97736 
 2013 10.55913 
 2014 11.16255 
 2015 12.22395 
 2016 12.71977 
 2017 12.46485 
 2018 11.90284