# year    value 
 1980 -8.33807 
 1981 -8.049395 
 1982 -8.119672 
 1983 -8.187352 
 1984 -8.320878 
 1985 -8.31714 
 1986 -7.937222 
 1987 -8.096548 
 1988 -7.982693 
 1989 -7.757991 
 1990 -7.355921 
 1991 -7.813268 
 1992 -7.868894 
 1993 -8.013412 
 1994 -8.099541 
 1995 -7.764443 
 1996 -7.787431 
 1997 -7.873141 
 1998 -7.674086 
 1999 -7.766352 
 2000 -7.877444 
 2001 -7.329125 
 2002 -7.610486 
 2003 -7.116254 
 2004 -7.039395 
 2005 -7.525425