# year    value 
 1980     0.28 
 1981     0.19 
 1982      0.2 
 1983     0.35 
 1984     0.13 
 1985      0.1 
 1986     0.28 
 1987     0.52 
 1988     0.58 
 1989     0.15 
 1990     0.35 
 1991      0.5 
 1992     0.39 
 1993     0.44 
 1994     0.19 
 1995     0.73 
 1996     0.56 
 1997     0.52 
 1998     1.05 
 1999      0.6 
 2000     0.28 
 2001     0.55 
 2002     0.65 
 2003     0.62 
 2004      0.4 
 2005      0.9 
 2006      0.7 
 2007     0.42 
 2008     0.59 
 2009     0.82 
 2010      0.8 
 2011     0.61 
 2012     0.52 
 2013     0.73 
 2014     0.77 
 2015     1.13 
 2016     1.08 
 2017     1.25 
 2018     0.66