# year    value 
 1980 24.93642 
 1981 24.65862 
 1982 24.75938 
 1983 25.05539 
 1984 24.81178 
 1985  24.8399 
 1986 24.74744 
 1987 25.31543 
 1988   25.205 
 1989 24.83257 
 1990 25.23436 
 1991 25.07463 
 1992  24.6997 
 1993 24.97619 
 1994 25.18531 
 1995 25.37078 
 1996 25.09669 
 1997 25.53544 
 1998 25.36829 
 1999 24.96582 
 2000 25.09096 
 2001 25.04551 
 2002 25.51518 
 2003 25.36356 
 2004  25.3847 
 2005 25.50207 
 2006 25.38944 
 2007  25.4723 
 2008 25.41849 
 2009 25.57265 
 2010 25.22805 
 2011 25.15794 
 2012 25.60801 
 2013 25.49944 
 2014 25.74318 
 2015 25.88139 
 2016 25.41367 
 2017  25.5172 
 2018 25.52851