# year    value 
 1980  14.8506 
 1981 14.71805 
 1982 14.69223 
 1983 14.37086 
 1984 13.82911 
 1985 14.37507 
 1986 14.38196 
 1987 14.24158 
 1988 14.30301 
 1989 14.58566 
 1990   14.317 
 1991  14.6346 
 1992 14.07561 
 1993 14.33016 
 1994 14.53887 
 1995 14.05885 
 1996 14.38577 
 1997 14.53762 
 1998 14.62976 
 1999 14.31795 
 2000 14.11718 
 2001 14.14174 
 2002 14.42346 
 2003 14.60529 
 2004 14.38577 
 2005 14.52753 
 2006 14.07434 
 2007 14.47918 
 2008  14.5327 
 2009 14.95416 
 2010  14.7508 
 2011 14.28459 
 2012 14.44538 
 2013 14.85009 
 2014 14.48196 
 2015 14.88358 
 2016 14.67039 
 2017 14.82591 
 2018 15.17805