# year    value 
 1979 -27.64626 
 1980 -23.18911 
 1981 -22.49119 
 1982 -24.07151 
 1983 -24.15527 
 1984 -23.6639 
 1985 -25.29466 
 1986 -23.52485 
 1987 -25.25611 
 1988 -23.95807 
 1989 -23.31926 
 1990 -25.1312 
 1991 -24.48266 
 1992 -23.9004 
 1993 -22.90659 
 1994 -25.68572 
 1995 -22.3737 
 1996 -23.21429 
 1997 -24.16677 
 1998 -24.94603 
 1999 -23.99187 
 2000 -22.9142 
 2001 -24.39804 
 2002 -23.49259 
 2003 -23.27688 
 2004 -23.2689 
 2005 -23.22558 
 2006 -22.86678 
 2007 -21.75383 
 2008 -22.28375 
 2009 -22.98435 
 2010 -23.28031 
 2011 -22.80451 
 2012 -21.73602 
 2013 -23.79025 
 2014 -23.05555 
 2015 -22.64136 
 2016 -21.05904 
 2017 -22.1068 
 2018 -21.07125 
 2019 -22.04678