# year    value 
 1979 -10.85495 
 1980 -10.67939 
 1981 -9.149776 
 1982 -11.03133 
 1983 -10.3854 
 1984 -9.64016 
 1985 -11.51622 
 1986 -11.18481 
 1987 -11.45193 
 1988 -9.695393 
 1989 -9.761399 
 1990 -7.471091 
 1991 -9.637135 
 1992 -10.5694 
 1993 -9.442913 
 1994 -9.649474 
 1995 -9.434253 
 1996 -9.743506 
 1997 -9.195889 
 1998 -10.0804 
 1999 -10.87125 
 2000 -9.385491 
 2001 -10.29855 
 2002 -9.468953 
 2003 -9.452955 
 2004 -9.865665 
 2005 -8.42324 
 2006 -10.81282 
 2007 -9.113178 
 2008 -9.306856 
 2009 -9.897934 
 2010 -8.965014 
 2011 -8.547241 
 2012 -9.575544 
 2013 -9.813559 
 2014 -8.364957 
 2015 -8.765141 
 2016 -7.551275 
 2017 -8.193486 
 2018  -9.4452