# year    value 
 1980     0.25 
 1981     0.24 
 1982     0.19 
 1983     0.48 
 1984    -0.08 
 1985     0.19 
 1986    -0.12 
 1987     0.58 
 1988     0.19 
 1989     0.38 
 1990     0.51 
 1991     0.07 
 1992    -0.07 
 1993     0.23 
 1994     0.35 
 1995     0.63 
 1996     0.58 
 1997     0.48 
 1998      1.1 
 1999     0.63 
 2000     0.34 
 2001     0.75 
 2002     0.59 
 2003     0.84 
 2004     0.41 
 2005     0.88 
 2006     0.95 
 2007     0.52 
 2008      0.6 
 2009     0.98 
 2010      0.7 
 2011     0.79 
 2012     0.82 
 2013     0.59 
 2014     0.95 
 2015     1.37 
 2016     1.31 
 2017     1.26 
 2018     0.72