# year    value 
 1979 12.74631 
 1980 12.59531 
 1981 12.95479 
 1982 11.78454 
 1983 12.99071 
 1984 11.48354 
 1985  10.2671 
 1986 11.34978 
 1987 12.65821 
 1988  12.5622 
 1989 12.41768 
 1990 13.29076 
 1991 11.43198 
 1992 11.98982 
 1993 10.93153 
 1994 12.74553 
 1995 12.31867 
 1996 11.08624 
 1997 12.57146 
 1998 13.75254 
 1999 13.22973 
 2000 11.56357 
 2001 13.41442 
 2002 11.63828 
 2003 12.44302 
 2004 12.88044 
 2005 13.56507 
 2006 11.96354 
 2007 13.44103 
 2008 12.75115 
 2009 12.46656 
 2010 13.01355 
 2011 13.19721 
 2012 13.10661 
 2013 12.37107 
 2014 12.55497 
 2015  14.1572 
 2016 14.49408 
 2017 13.37136 
 2018   11.719