# year    value 
 1980 4.119974 
 1981 4.091438 
 1982 3.911843 
 1983 3.831205 
 1984 3.994576 
 1985 3.944861 
 1986 4.010529 
 1987 4.142299 
 1988 4.185066 
 1989 4.213456 
 1990  4.29247 
 1991 4.182835 
 1992 3.901101 
 1993 4.054501 
 1994 4.013937 
 1995 4.155398 
 1996 4.302146 
 1997 4.384704 
 1998  4.39215 
 1999 4.424167 
 2000  4.41731 
 2001 4.519935 
 2002 4.574814 
 2003 4.502167 
 2004 4.530258 
 2005  4.64887