# year    value 
 1980     0.57 
 1981     0.34 
 1982     0.14 
 1983     0.69 
 1984     0.25 
 1985     0.37 
 1986     0.58 
 1987     0.59 
 1988     0.69 
 1989     0.27 
 1990     0.65 
 1991     0.54 
 1992     0.73 
 1993     0.51 
 1994     0.37 
 1995     0.41 
 1996     0.44 
 1997     0.16 
 1998     1.14 
 1999     0.48 
 2000      0.2 
 2001     0.43 
 2002     0.94 
 2003     0.71 
 2004     0.55 
 2005     1.03 
 2006     0.38 
 2007     0.77 
 2008     0.21 
 2009     0.68 
 2010     1.04 
 2011     0.32 
 2012     0.43 
 2013     0.77 
 2014     0.76 
 2015      0.8 
 2016     1.31 
 2017     0.98 
 2018     0.96