# year    value 
 1980 0.2903124 
 1981 0.6513966 
 1982 0.1068276 
 1983 0.1409795 
 1984 -0.1856297 
 1985 -0.4896408 
 1986 0.3211252 
 1987 0.5110509 
 1988 0.5198101 
 1989 0.2833487 
 1990 0.3548246 
 1991 0.4788622 
 1992 0.328862 
 1993 0.3057592 
 1994 0.5066007 
 1995 0.8655085 
 1996 0.2623624 
 1997 0.5518602 
 1998 0.6838309 
 1999 1.045385 
 2000 0.4197737 
 2001 0.3226874 
 2002 0.9926776 
 2003 0.9667683 
 2004 0.9210105 
 2005 0.4022122 
 2006 0.8844139 
 2007 1.206999 
 2008 0.2779883 
 2009 0.7961357 
 2010 0.8300216 
 2011 0.4052029 
 2012 0.3000131 
 2013 0.4694099 
 2014 0.9100552 
 2015 1.613613 
 2016 1.641902 
 2017 1.565804 
 2018 1.338909