# year    value 
 1980 -5.721459 
 1981 -5.682655 
 1982 -5.69097 
 1983 -6.095275 
 1984 -5.879434 
 1985 -5.812465 
 1986 -5.787316 
 1987 -5.762856 
 1988 -5.588102 
 1989 -5.665294 
 1990 -5.587896 
 1991 -5.468865 
 1992 -6.011611 
 1993 -5.853506 
 1994 -5.783041 
 1995 -5.574867 
 1996 -5.514882 
 1997 -5.51765 
 1998 -5.475712 
 1999 -5.393945 
 2000 -5.308004 
 2001 -5.325912 
 2002 -5.249813 
 2003 -5.218349 
 2004 -5.328127 
 2005 -5.268612