# year    value 
 1980     0.51 
 1981     0.32 
 1982     0.38 
 1983      0.5 
 1984     0.28 
 1985     0.47 
 1986     0.16 
 1987     0.43 
 1988     0.57 
 1989     0.48 
 1990     0.56 
 1991     0.39 
 1992    -0.25 
 1993     0.26 
 1994     0.34 
 1995     0.35 
 1996     0.59 
 1997     0.45 
 1998     0.55 
 1999     0.82 
 2000     0.29 
 2001     0.32 
 2002     0.41 
 2003     0.39 
 2004     0.65 
 2005     0.58 
 2006     0.95 
 2007     0.74 
 2008     0.89 
 2009     0.53 
 2010      0.4 
 2011     0.86 
 2012     0.98 
 2013     0.85 
 2014     1.22 
 2015     0.75 
 2016     0.57 
 2017     1.07 
 2018     0.85