# year    value 
 1980     1.24 
 1981     2.48 
 1982      0.7 
 1983     0.94 
 1984     1.57 
 1985    -0.46 
 1986     1.18 
 1987    -0.53 
 1988     1.07 
 1989     1.83 
 1990    -0.33 
 1991     0.33 
 1992     1.05 
 1993     2.21 
 1994    -0.68 
 1995     2.59 
 1996     1.35 
 1997     0.53 
 1998    -0.14 
 1999     0.92 
 2000     1.93 
 2001      0.6 
 2002      1.3 
 2003      1.5 
 2004     1.76 
 2005     1.66 
 2006     1.43 
 2007     2.97 
 2008     2.63 
 2009     1.48 
 2010     0.85 
 2011     1.41 
 2012      2.8 
 2013     0.81 
 2014     2.18 
 2015     2.79 
 2016     4.22 
 2017     2.76 
 2018     3.79