# year    value 
 1980     0.53 
 1981     1.09 
 1982     0.29 
 1983      1.4 
 1984     0.17 
 1985    -0.87 
 1986     0.44 
 1987     0.97 
 1988     0.72 
 1989     1.17 
 1990     1.31 
 1991     0.84 
 1992     1.29 
 1993     0.77 
 1994     0.38 
 1995     1.73 
 1996      0.2 
 1997     1.23 
 1998     1.61 
 1999     2.05 
 2000     1.67 
 2001     0.71 
 2002     2.23 
 2003     0.53 
 2004     1.72 
 2005     0.61 
 2006     0.68 
 2007     2.37 
 2008     0.46 
 2009     0.97 
 2010      0.5 
 2011      0.5 
 2012     0.41 
 2013      0.7 
 2014     0.94 
 2015     1.92 
 2016      2.7 
 2017     1.87 
 2018     1.21