# year    value 
 1980 -16.95845 
 1981 -16.88782 
 1982 -16.94036 
 1983 -16.97517 
 1984 -16.92175 
 1985 -16.9722 
 1986 -16.73631 
 1987 -16.75271 
 1988  -16.547 
 1989 -16.54944 
 1990 -16.44975 
 1991 -16.38508 
 1992 -16.51317 
 1993 -16.37862 
 1994 -16.74597 
 1995 -16.89783 
 1996 -16.49027 
 1997 -16.1819 
 1998 -16.15857 
 1999 -16.28844 
 2000 -16.13011 
 2001 -15.67135 
 2002 -15.88904 
 2003 -15.4751 
 2004 -15.54202 
 2005 -15.27803