# year    value 
 1980     0.38 
 1981     0.21 
 1982     0.16 
 1983     0.33 
 1984     0.09 
 1985     0.24 
 1986      0.2 
 1987     0.77 
 1988     0.23 
 1989     0.47 
 1990     0.52 
 1991     0.28 
 1992      0.1 
 1993      0.5 
 1994     0.27 
 1995     0.56 
 1996      0.4 
 1997     0.81 
 1998     0.93 
 1999     0.55 
 2000     0.49 
 2001     0.76 
 2002      0.8 
 2003      0.9 
 2004     0.77 
 2005      0.8 
 2006     0.78 
 2007     0.67 
 2008     0.66 
 2009     0.92 
 2010     0.99 
 2011     0.74 
 2012      0.9 
 2013     0.79 
 2014      0.9 
 2015     1.39 
 2016     1.21 
 2017     1.08 
 2018     1.04