# year    value 
 1979 25.87304 
 1980 25.96181 
 1981 25.80527 
 1982 25.92573 
 1983  26.5037 
 1984 25.70047 
 1985 25.90533 
 1986 25.83911 
 1987 26.03336 
 1988 26.30114 
 1989 25.64451 
 1990 25.99096 
 1991 26.15617 
 1992 26.05942 
 1993 25.76374 
 1994 25.99047 
 1995 26.12422 
 1996 25.96052 
 1997 25.81763 
 1998 26.75233 
 1999 26.00109 
 2000 25.57459 
 2001 25.84389 
 2002 25.96076 
 2003 26.46286 
 2004 26.25669 
 2005 26.59024 
 2006 26.26053 
 2007 26.42505 
 2008 25.98119 
 2009 26.14371 
 2010 26.55817 
 2011  25.9188 
 2012 25.98343 
 2013 26.60429 
 2014 26.23812 
 2015 26.49407 
 2016 27.03905 
 2017  26.3838 
 2018  26.4235 
 2019 26.95231