# year    value 
 1980     0.57 
 1981    -0.35 
 1982    -0.07 
 1983     0.81 
 1984    -0.31 
 1985    -0.51 
 1986    -0.16 
 1987     0.07 
 1988      0.9 
 1989     0.47 
 1990     1.19 
 1991      0.5 
 1992    -0.15 
 1993    -0.22 
 1994     0.65 
 1995     0.93 
 1996    -0.16 
 1997     0.56 
 1998        1 
 1999        1 
 2000    -0.26 
 2001     1.28 
 2002     0.59 
 2003     0.67 
 2004     0.93 
 2005     1.11 
 2006        1 
 2007     1.03 
 2008     1.08 
 2009     0.51 
 2010      1.2 
 2011     0.78 
 2012     0.97 
 2013     1.14 
 2014     1.17 
 2015     1.09 
 2016     0.68 
 2017     1.05 
 2018     0.99