# year    value 
 1980 -2.15916 
 1981 -1.75641 
 1982 -2.265697 
 1983 -3.089227 
 1984 -3.218014 
 1985 -2.532993 
 1986 -2.273136 
 1987 -1.278806 
 1988 -1.604002 
 1989 -2.034477 
 1990 -1.463871 
 1991 -1.903799 
 1992 -2.338774 
 1993 -1.788839 
 1994 -1.795927 
 1995 -2.309239 
 1996 -2.478843 
 1997 -2.053288 
 1998 -1.946735 
 1999 -0.609877 
 2000 -2.246221 
 2001 -1.278567 
 2002 -1.172921 
 2003 -1.427603 
 2004 -1.283584 
 2005 -1.930652 
 2006 -1.137455 
 2007 -1.09822 
 2008 -2.861642 
 2009 -0.5405466 
 2010 -1.172117 
 2011 -2.169721 
 2012 -2.736727 
 2013 -1.718869 
 2014 -2.044034 
 2015 -1.446692 
 2016 -1.498815 
 2017 -0.553894 
 2018 -1.400905