# year    value 
 1979 -12.12318 
 1980 -11.28014 
 1981 -10.78853 
 1982 -11.83101 
 1983 -11.88823 
 1984 -11.31065 
 1985 -11.9145 
 1986 -11.59963 
 1987 -12.12928 
 1988 -10.83422 
 1989 -10.87474 
 1990 -9.087832 
 1991 -10.88617 
 1992 -11.66471 
 1993 -10.71941 
 1994 -10.65446 
 1995 -9.791883 
 1996 -10.31624 
 1997 -9.932888 
 1998 -10.47416 
 1999 -11.39409 
 2000 -9.95795 
 2001 -11.07589 
 2002 -10.47469 
 2003 -9.922247 
 2004 -11.25643 
 2005 -9.499988 
 2006 -10.65757 
 2007 -9.715649 
 2008 -10.2399 
 2009 -10.89292 
 2010 -9.023164 
 2011 -9.289947 
 2012 -9.98709 
 2013 -10.72491 
 2014 -9.171402 
 2015 -9.412291 
 2016 -8.45736 
 2017 -9.17173 
 2018 -10.6419