# year    value 
 1980     0.03 
 1981     0.88 
 1982     0.09 
 1983     0.34 
 1984     0.32 
 1985     0.12 
 1986     0.29 
 1987     0.13 
 1988     0.42 
 1989     0.76 
 1990     1.11 
 1991     0.34 
 1992     0.58 
 1993     0.59 
 1994     0.79 
 1995     0.49 
 1996     0.41 
 1997     1.02 
 1998     1.07 
 1999     0.48 
 2000     1.26 
 2001     1.16 
 2002     1.17 
 2003     0.81 
 2004     1.18 
 2005     1.14 
 2006     0.76 
 2007     1.28 
 2008     1.42 
 2009     1.15 
 2010     0.89 
 2011     0.97 
 2012     1.12 
 2013     1.14 
 2014     1.51 
 2015     1.58 
 2016     1.91 
 2017     1.71 
 2018     1.83