# year    value 
 1980 -2.993827 
 1981 -3.126102 
 1982 -3.133831 
 1983 -3.245837 
 1984 -3.129317 
 1985 -3.246679 
 1986 -3.139455 
 1987 -2.941875 
 1988 -2.971207 
 1989 -2.93725 
 1990 -2.827453 
 1991 -3.017678 
 1992 -3.267479 
 1993 -3.076548 
 1994 -3.110518 
 1995 -3.042099 
 1996 -2.719739 
 1997 -2.837423 
 1998 -2.621346 
 1999 -2.664136 
 2000 -2.737535 
 2001 -2.61144 
 2002 -2.500354 
 2003 -2.680085 
 2004 -2.501088 
 2005 -2.527452