# year    value 
 1980 2.206568 
 1981 2.298432 
 1982 2.190227 
 1983 2.009609 
 1984 2.109289 
 1985  2.11372 
 1986 2.099977 
 1987 2.238562 
 1988 2.346409 
 1989 2.222941 
 1990 2.396722 
 1991 2.277524 
 1992 2.034586 
 1993 2.151235 
 1994 2.067715 
 1995 2.195055 
 1996 2.335945 
 1997 2.431053 
 1998 2.447422 
 1999 2.454688 
 2000 2.533653 
 2001 2.514203 
 2002 2.667223 
 2003 2.561835 
 2004 2.582316 
 2005 2.707558