# year    value 
 1979 -9.978135 
 1980 -9.219447 
 1981 -8.285146 
 1982 -9.997349 
 1983 -8.913116 
 1984 -9.44853 
 1985 -9.263797 
 1986 -9.143703 
 1987 -9.898709 
 1988 -8.545463 
 1989 -8.898599 
 1990 -9.158221 
 1991 -8.58326 
 1992 -9.652159 
 1993 -8.868395 
 1994 -9.152984 
 1995 -8.183786 
 1996 -9.387838 
 1997 -8.633833 
 1998 -9.318648 
 1999 -9.627787 
 2000 -9.018655 
 2001 -8.975242 
 2002 -8.484359 
 2003 -8.151212 
 2004 -8.917025 
 2005 -7.770084 
 2006 -8.610964 
 2007 -7.920626 
 2008 -8.509476 
 2009 -8.696059 
 2010 -8.186244 
 2011 -8.232822 
 2012 -8.482535 
 2013 -8.295476 
 2014 -7.778784 
 2015 -7.830636 
 2016 -6.989635 
 2017 -7.482008 
 2018 -7.641749 
 2019 -21.54292