# year    value 
 1980 13.49118 
 1981 13.70606 
 1982 13.25632 
 1983 13.64671 
 1984 13.23072 
 1985  13.2429 
 1986 13.40142 
 1987 13.61527 
 1988 13.76599 
 1989 13.55577 
 1990 13.83999 
 1991 13.68912 
 1992 13.34824 
 1993 13.51685 
 1994 13.68648 
 1995 13.96271 
 1996 13.54716 
 1997 13.77532 
 1998 14.16729 
 1999 13.88103 
 2000 13.73823 
 2001   13.974 
 2002  14.0881 
 2003 14.11175 
 2004 13.96429 
 2005 14.30283 
 2006 14.20238 
 2007 14.30794 
 2008 14.08151 
 2009 14.10898 
 2010 14.43131 
 2011 14.09257 
 2012 14.20069 
 2013 14.24181 
 2014 14.25492 
 2015 14.57267 
 2016 14.78337 
 2017 14.61279 
 2018 14.40009