# year    value 
 1979 13.14614 
 1980   13.458 
 1981 13.73629 
 1982 13.17062 
 1983 13.44855 
 1984 13.40714 
 1985 13.29687 
 1986 13.53381 
 1987 13.38379 
 1988 13.75594 
 1989 13.53601 
 1990  14.1181 
 1991 13.66702 
 1992 13.43521 
 1993 13.59918 
 1994 13.77293 
 1995  13.7953 
 1996 13.47524 
 1997 13.66397 
 1998 14.21585 
 1999 13.66766 
 2000 14.04399 
 2001 14.00931 
 2002 14.03893 
 2003 13.94294 
 2004 13.93357 
 2005 14.32288 
 2006 13.97788 
 2007 14.33801 
 2008 14.17664 
 2009  13.9845 
 2010 14.56488 
 2011 14.01897 
 2012 14.29059 
 2013 14.15199 
 2014 14.38546 
 2015 14.41666 
 2016 15.04405 
 2017 14.63197 
 2018 14.39346