# year    value 
 1979  24.4516 
 1980 24.52103 
 1981 24.31498 
 1982 24.13492 
 1983 24.33046 
 1984  24.1559 
 1985 24.20431 
 1986 24.23311 
 1987 24.76798 
 1988 24.59226 
 1989 24.23082 
 1990 24.65902 
 1991 24.49035 
 1992 24.14903 
 1993 24.46577 
 1994 24.48645 
 1995 24.61056 
 1996 24.54053 
 1997 24.52804 
 1998  25.0903 
 1999 24.65042 
 2000 24.52263 
 2001 24.77068 
 2002 24.89187 
 2003 24.91947 
 2004 24.84079 
 2005 25.00948 
 2006 24.96311 
 2007 24.90257 
 2008 24.73211 
 2009 25.18227 
 2010 25.44309 
 2011 24.85034 
 2012 24.92665 
 2013 25.01536 
 2014 25.08043 
 2015 25.23085 
 2016 25.48306 
 2017 25.28113 
 2018 25.23104