# year    value 
 1980     0.48 
 1981     0.69 
 1982     0.29 
 1983     0.76 
 1984     0.27 
 1985    -0.17 
 1986     0.37 
 1987      0.4 
 1988      0.7 
 1989     0.63 
 1990     0.56 
 1991     0.61 
 1992      0.6 
 1993     0.65 
 1994     0.14 
 1995     1.08 
 1996     0.42 
 1997     0.61 
 1998     1.06 
 1999     1.12 
 2000     0.98 
 2001     0.57 
 2002     1.26 
 2003     0.72 
 2004     1.15 
 2005     0.85 
 2006     0.84 
 2007     1.54 
 2008     0.72 
 2009      0.9 
 2010     0.86 
 2011     0.63 
 2012     0.79 
 2013     0.91 
 2014     0.88 
 2015     1.29 
 2016      2.1 
 2017     1.54 
 2018      1.3