# year    value 
 1980     0.49 
 1981     0.29 
 1982     0.36 
 1983      0.5 
 1984     0.29 
 1985      0.5 
 1986     0.17 
 1987     0.46 
 1988     0.54 
 1989     0.49 
 1990     0.53 
 1991     0.38 
 1992    -0.21 
 1993     0.27 
 1994     0.34 
 1995     0.35 
 1996     0.58 
 1997     0.43 
 1998     0.55 
 1999     0.83 
 2000     0.26 
 2001     0.34 
 2002      0.4 
 2003     0.41 
 2004     0.66 
 2005     0.59 
 2006     0.92 
 2007     0.71 
 2008     0.89 
 2009     0.47 
 2010     0.42 
 2011     0.85 
 2012     0.94 
 2013     0.83 
 2014     1.17 
 2015      0.7 
 2016     0.63 
 2017     1.03 
 2018     0.83