# year    value 
 1979  24.6632 
 1980 24.76186 
 1981 24.51454 
 1982 24.56582 
 1983 24.83995 
 1984 24.51011 
 1985   24.489 
 1986  24.4127 
 1987 25.11056 
 1988 24.98684 
 1989 24.71253 
 1990  24.9746 
 1991 24.75289 
 1992  24.4154 
 1993 24.79389 
 1994 24.98825 
 1995 25.11568 
 1996 24.86973 
 1997 25.38246 
 1998 25.16404 
 1999 24.67573 
 2000 24.77085 
 2001 24.79377 
 2002 25.29688 
 2003 25.17419 
 2004 25.15921 
 2005 25.32354 
 2006 25.22736 
 2007 25.32546 
 2008 25.34621 
 2009 25.44853 
 2010 25.09905 
 2011 24.99814 
 2012 25.53811 
 2013 25.43048 
 2014 25.59637 
 2015 25.98107 
 2016 25.41138 
 2017 25.52398 
 2018 25.54716