# year    value 
 1980  12.4254 
 1981 12.72112 
 1982 11.42598 
 1983 12.72182 
 1984 11.20716 
 1985 10.03729 
 1986 11.19483 
 1987 12.40266 
 1988 12.23511 
 1989 12.12154 
 1990 13.08215 
 1991 11.18396 
 1992 11.73266 
 1993 10.58612 
 1994 12.62186 
 1995 12.17732 
 1996 11.00019 
 1997 12.16086 
 1998 13.44273 
 1999 12.86856 
 2000 11.20146 
 2001 13.12053 
 2002 11.32127 
 2003 12.07678 
 2004 12.61921 
 2005 13.30987 
 2006 11.66283 
 2007 13.03133 
 2008 12.42657 
 2009 12.27451 
 2010 12.69321 
 2011 12.78128 
 2012 12.76726 
 2013 12.33594 
 2014 12.33767 
 2015 13.88817 
 2016 14.37417 
 2017 13.07565 
 2018 11.53303