# year    value 
 1980 -10.47311 
 1981 -10.02279 
 1982   -10.26 
 1983 -10.30867 
 1984 -10.41016 
 1985 -10.72627 
 1986 -10.03494 
 1987 -10.30993 
 1988 -10.04922 
 1989 -10.17293 
 1990 -10.12778 
 1991 -10.02146 
 1992 -10.15307 
 1993 -10.90133 
 1994 -10.02543 
 1995 -10.72572 
 1996 -9.95117 
 1997 -9.691251 
 1998 -9.385943 
 1999 -10.23375 
 2000 -9.936114 
 2001 -9.853162 
 2002 -10.09031 
 2003 -9.429813 
 2004 -9.821938 
 2005 -9.372614