# year    value 
 1980 -16.27672 
 1981 -16.15698 
 1982 -16.1361 
 1983 -16.35773 
 1984 -16.47154 
 1985 -16.26357 
 1986 -16.09244 
 1987 -15.95099 
 1988 -15.87598 
 1989 -15.93039 
 1990 -15.79065 
 1991 -15.78213 
 1992 -15.85027 
 1993 -15.86704 
 1994 -15.92226 
 1995 -16.18587 
 1996 -15.85476 
 1997  -15.599 
 1998 -15.39589 
 1999 -15.48803 
 2000 -15.43113 
 2001 -15.01418 
 2002 -15.04776 
 2003 -14.71841 
 2004 -14.75497 
 2005 -14.47815