# year    value 
 1980     0.78 
 1981    -0.47 
 1982     0.26 
 1983     0.59 
 1984    -0.04 
 1985     -0.2 
 1986    -0.14 
 1987     0.25 
 1988     0.67 
 1989     0.48 
 1990     0.98 
 1991     0.37 
 1992    -0.21 
 1993    -0.15 
 1994     0.48 
 1995     0.83 
 1996     0.29 
 1997     0.36 
 1998      1.5 
 1999     1.11 
 2000     0.16 
 2001     1.14 
 2002     0.77 
 2003     0.72 
 2004      0.7 
 2005     1.18 
 2006     1.56 
 2007     0.82 
 2008     1.05 
 2009     0.73 
 2010     1.14 
 2011     0.98 
 2012     0.33 
 2013     1.05 
 2014     1.08 
 2015     1.16 
 2016     0.93 
 2017     1.33 
 2018     0.54