# year    value 
 1980 24.94843 
 1981 24.69088 
 1982 24.70917 
 1983 24.89337 
 1984 24.65212 
 1985  24.7433 
 1986 24.68307 
 1987 25.23021 
 1988 24.71607 
 1989 24.94012 
 1990 25.21469 
 1991 24.75058 
 1992 24.59633 
 1993 25.08222 
 1994 24.81848 
 1995 25.05059 
 1996  24.8754 
 1997 25.29939 
 1998 25.39646 
 1999 25.04981 
 2000 24.94892 
 2001 25.23037 
 2002   25.302 
 2003 25.40796 
 2004 25.28275 
 2005 25.32389 
 2006 25.26491 
 2007 25.23415 
 2008 25.19808 
 2009 25.47645 
 2010  25.5727 
 2011 25.19326 
 2012 25.38512 
 2013 25.19095 
 2014 25.33385 
 2015 25.75333 
 2016 25.59788 
 2017 25.45636 
 2018 25.31537