# year    value 
 1980 0.5038481 
 1981 0.5599616 
 1982 0.401437 
 1983 0.1811415 
 1984 0.3717601 
 1985 0.5466224 
 1986 0.4636763 
 1987 0.5853964 
 1988 0.6760839 
 1989 0.7063718 
 1990 0.7023088 
 1991 0.6591812 
 1992 0.2160591 
 1993  0.47619 
 1994 0.7127424 
 1995 0.7890518 
 1996 0.783483 
 1997 0.9487568 
 1998 0.9608963 
 1999  1.06543 
 2000 1.132314 
 2001 1.156701 
 2002 1.243309 
 2003 1.244099 
 2004 1.203023 
 2005 1.257641