# year    value 
 1980    -0.23 
 1981     0.92 
 1982     0.13 
 1983     0.42 
 1984     0.11 
 1985     0.23 
 1986     0.62 
 1987     0.11 
 1988     0.47 
 1989     0.88 
 1990     1.32 
 1991     0.52 
 1992     0.39 
 1993     0.46 
 1994     0.79 
 1995      0.7 
 1996    -0.12 
 1997     0.95 
 1998     1.12 
 1999     0.83 
 2000     1.66 
 2001     1.62 
 2002     1.01 
 2003     0.63 
 2004     1.21 
 2005     1.19 
 2006     1.31 
 2007      1.5 
 2008     1.68 
 2009     1.01 
 2010     1.04 
 2011     0.96 
 2012      1.8 
 2013        1 
 2014     1.47 
 2015     1.54 
 2016     2.04 
 2017     1.74 
 2018     1.67