# year    value 
 1980 4.467777 
 1981 4.605782 
 1982 4.594661 
 1983 4.379244 
 1984 4.432254 
 1985  4.56495 
 1986 4.484282 
 1987 4.463063 
 1988 4.564926 
 1989 4.570557 
 1990 4.616818 
 1991 4.633049 
 1992 4.394228 
 1993 4.417674 
 1994 4.554399 
 1995 4.605419 
 1996 4.618252 
 1997 4.716206 
 1998 4.745372 
 1999 4.775913 
 2000 4.793935 
 2001 4.857049 
 2002 4.873561 
 2003 4.908348 
 2004  4.84539 
 2005 4.956425