# year    value 
 1980 -16.12355 
 1981 -15.99277 
 1982 -15.95539 
 1983  -16.219 
 1984 -16.37039 
 1985 -16.10435 
 1986 -15.94777 
 1987 -15.77085 
 1988 -15.72521 
 1989 -15.7913 
 1990 -15.64256 
 1991 -15.64665 
 1992 -15.70132 
 1993 -15.75209 
 1994 -15.73719 
 1995 -16.0259 
 1996 -15.71197 
 1997 -15.46803 
 1998 -15.22452 
 1999 -15.30819 
 2000 -15.27407 
 2001 -14.86652 
 2002 -14.85874 
 2003 -14.54839 
 2004 -14.57813 
 2005 -14.29843