# year    value 
 1979 13.94104 
 1980 13.92688 
 1981 13.92208 
 1982 13.96079 
 1983 14.77268 
 1984  13.5836 
 1985 13.35778 
 1986 13.70424 
 1987 14.26503 
 1988 14.19187 
 1989 13.86773 
 1990 14.03368 
 1991 14.13726 
 1992 13.84126 
 1993 13.73722 
 1994 14.10563 
 1995 14.35957 
 1996  13.9828 
 1997 13.92075 
 1998 15.43905 
 1999 13.99795 
 2000 13.88876 
 2001 14.17186 
 2002 14.31606 
 2003 14.70076 
 2004 14.32165 
 2005 14.60125 
 2006 14.43572 
 2007 14.82922 
 2008 13.95308 
 2009 14.11351 
 2010 15.14846 
 2011 14.05775 
 2012 14.17898 
 2013 14.49853 
 2014 14.53096 
 2015 14.56904 
 2016 15.48451 
 2017 14.96962 
 2018 14.39201