# year    value 
 1980 0.4664382 
 1981 0.611995 
 1982 0.2991785 
 1983 0.002546292 
 1984 0.2086067 
 1985 0.4223238 
 1986 0.306191 
 1987 0.6483995 
 1988 0.7255879 
 1989 0.6867124 
 1990 1.097592 
 1991 0.9698042 
 1992 0.4254611 
 1993 0.5934966 
 1994 0.6748483 
 1995 0.9772835 
 1996 1.124792 
 1997 1.136342 
 1998 1.357428 
 1999 1.455599 
 2000 1.516609 
 2001 1.517267 
 2002 1.836394 
 2003  1.71393 
 2004 1.808329 
 2005 1.832844