# year    value 
 1980     0.33 
 1981     0.55 
 1982     0.09 
 1983     0.43 
 1984     0.22 
 1985     0.17 
 1986     0.44 
 1987     0.27 
 1988     0.65 
 1989     0.49 
 1990     0.98 
 1991     0.63 
 1992     0.33 
 1993     0.46 
 1994     0.54 
 1995     0.73 
 1996     0.31 
 1997     0.59 
 1998     1.09 
 1999     0.65 
 2000     0.97 
 2001     0.91 
 2002     0.94 
 2003     0.85 
 2004      0.8 
 2005     1.09 
 2006     0.88 
 2007     1.15 
 2008     0.96 
 2009     0.81 
 2010     1.38 
 2011     0.94 
 2012     1.16 
 2013     0.88 
 2014      1.2 
 2015     1.26 
 2016     1.81 
 2017      1.4 
 2018     1.18