# year    value 
 1980 14.24856 
 1981 13.94717 
 1982 14.13996 
 1983 14.17749 
 1984  13.9157 
 1985 14.20248 
 1986 13.73921 
 1987 14.14413 
 1988 14.20541 
 1989 14.11033 
 1990 14.30678 
 1991 14.04914 
 1992 13.30011 
 1993 13.91165 
 1994 14.11029 
 1995 14.08734 
 1996 14.19446 
 1997 14.12821 
 1998 14.13145 
 1999 14.43387 
 2000 13.85648 
 2001 13.92106 
 2002 14.32583 
 2003 14.17909 
 2004  14.3026 
 2005 14.14904 
 2006 14.75082 
 2007 14.50336 
 2008 14.62067 
 2009 14.16846 
 2010 14.06841 
 2011 14.60225 
 2012 14.74638 
 2013 14.50046 
 2014 15.03496 
 2015 14.22763 
 2016 14.21913 
 2017 14.65416 
 2018 14.49213