# year    value 
 1980 25.54755 
 1981 25.15557 
 1982 25.21237 
 1983 25.87993 
 1984  25.4107 
 1985 25.09253 
 1986 25.38254 
 1987 25.68955 
 1988 25.62251 
 1989 25.70224 
 1990 25.56952 
 1991 25.42929 
 1992  25.4566 
 1993 25.19717 
 1994 25.31165 
 1995 25.71743 
 1996 25.52856 
 1997 25.27132 
 1998 25.80211 
 1999 25.49395 
 2000 25.23167 
 2001  25.5247 
 2002 25.43054 
 2003 25.73176 
 2004 25.62766 
 2005 25.85539 
 2006 25.50748 
 2007 25.77164 
 2008 25.22236 
 2009 25.49054 
 2010 25.83125 
 2011 25.39448 
 2012 25.60441 
 2013 25.72683 
 2014 25.80265 
 2015 25.65825 
 2016 26.35144 
 2017 25.98489 
 2018 25.70275