# year    value 
 1980 4.536969 
 1981   4.6753 
 1982 4.662371 
 1983 4.447592 
 1984 4.501008 
 1985 4.637207 
 1986 4.566598 
 1987 4.543736 
 1988 4.643298 
 1989 4.649131 
 1990 4.694694 
 1991 4.712236 
 1992 4.470952 
 1993 4.500296 
 1994  4.62903 
 1995 4.682467 
 1996 4.692544 
 1997 4.790478 
 1998 4.822666 
 1999 4.865262 
 2000 4.865331 
 2001 4.951084 
 2002 4.958057 
 2003 4.993226 
 2004 4.924483 
 2005 5.032242