# year    value 
 1980     0.05 
 1981      1.2 
 1982    -0.99 
 1983     0.79 
 1984    -0.22 
 1985      0.6 
 1986     0.25 
 1987    -0.13 
 1988     0.41 
 1989    -0.18 
 1990    -0.52 
 1991     1.11 
 1992    -1.31 
 1993     0.08 
 1994      0.4 
 1995      1.5 
 1996     0.62 
 1997     1.09 
 1998     0.21 
 1999     0.72 
 2000     0.72 
 2001     1.08 
 2002     1.36 
 2003     1.73 
 2004     1.09 
 2005     2.61 
 2006     1.47 
 2007     2.26 
 2008     1.69 
 2009     1.38 
 2010     2.31 
 2011     1.95 
 2012     1.71 
 2013      1.5 
 2014      1.2 
 2015      1.7 
 2016      2.4 
 2017     1.92 
 2018     2.27