# year    value 
 1980  24.9652 
 1981 24.84084 
 1982 24.94236 
 1983 25.52224 
 1984 24.73106 
 1985 24.88411 
 1986 24.82851 
 1987 25.06821 
 1988 25.34419 
 1989 24.66332 
 1990 24.99635 
 1991 25.18341 
 1992 25.07075 
 1993 24.78887 
 1994 25.04873 
 1995 25.17374 
 1996 24.98874 
 1997 24.86489 
 1998 25.81101 
 1999 25.04761 
 2000 24.64771 
 2001 24.88924 
 2002 25.01251 
 2003 25.50666 
 2004 25.28351 
 2005 25.60734 
 2006  25.3138 
 2007 25.46406 
 2008   25.003 
 2009 25.16971 
 2010 25.64117 
 2011 24.98416 
 2012 25.03157 
 2013 25.62197 
 2014 25.29481 
 2015 25.53243 
 2016 26.10748 
 2017 25.47883 
 2018 25.45165