# year    value 
 1980 13.34595 
 1981 13.79796 
 1982 13.09821 
 1983 12.84762 
 1984 13.45135 
 1985 13.22519 
 1986 13.05306 
 1987 13.22746 
 1988 13.19118 
 1989 13.15467 
 1990 13.19778 
 1991 13.12699 
 1992 13.10991 
 1993 13.07492 
 1994 13.59494 
 1995 13.33055 
 1996 13.05173 
 1997 13.76363 
 1998 13.92849 
 1999 13.90875 
 2000 14.18175 
 2001  14.1931 
 2002  14.2653 
 2003 13.40013 
 2004 14.65583 
 2005 13.97261 
 2006 14.21511 
 2007  14.4475 
 2008 14.88311 
 2009 14.39099 
 2010 14.15162 
 2011  13.8115 
 2012 14.11374 
 2013 14.43684 
 2014 13.78194 
 2015 14.18828 
 2016 14.73043 
 2017 14.27146 
 2018 14.96528