# year    value 
 1980 14.98428 
 1981 14.80925 
 1982 14.76389 
 1983 14.43166 
 1984 13.84834 
 1985 14.47592 
 1986 14.46456 
 1987  14.3201 
 1988 14.40644 
 1989 14.66294 
 1990 14.40688 
 1991  14.8808 
 1992 14.45322 
 1993 14.59303 
 1994 14.72024 
 1995 14.17089 
 1996 14.56072 
 1997 14.63251 
 1998   14.736 
 1999 14.42963 
 2000  14.2789 
 2001  14.2525 
 2002 14.58164 
 2003 14.71433 
 2004 14.49619 
 2005 14.60966 
 2006 14.08805 
 2007 14.61038 
 2008 14.56418 
 2009 15.11479 
 2010 14.89092 
 2011 14.56046 
 2012 14.64196 
 2013 14.92779 
 2014  14.6915 
 2015 15.09367 
 2016 14.87224 
 2017   15.016 
 2018 15.35267