# year    value 
 1980 0.5648294 
 1981 1.992265 
 1982 -1.034292 
 1983 1.083687 
 1984 -1.272475 
 1985 -2.03587 
 1986 0.4892748 
 1987 0.9247249 
 1988 -0.5944996 
 1989 -1.288414 
 1990 0.1765232 
 1991 -0.4924444 
 1992  1.76016 
 1993 -1.962035 
 1994 -0.2469731 
 1995 1.639622 
 1996 0.4103704 
 1997 -0.4302233 
 1998 1.061422 
 1999  1.22342 
 2000 1.954149 
 2001 -1.217276 
 2002 0.7111537 
 2003 1.027702 
 2004 0.1267058 
 2005 1.115224 
 2006 1.566887 
 2007 -0.235509 
 2008 -0.5174115 
 2009 0.05824029 
 2010 -1.276425 
 2011 -0.5266449 
 2012 1.090346 
 2013 0.02937802 
 2014 -0.7007461 
 2015 1.671761 
 2016 1.824109 
 2017 0.4275142 
 2018 0.348385