# year    value 
 1980 0.521163 
 1981 0.4768722 
 1982 0.2752611 
 1983 0.3070642 
 1984 0.4249504 
 1985 0.4049878 
 1986 0.4196611 
 1987 0.5076686 
 1988 0.6090423 
 1989 0.6543928 
 1990 0.7177652 
 1991 0.3429426 
 1992 0.3595211 
 1993 0.4374706 
 1994 0.4898295 
 1995 0.5544807 
 1996 0.6945068 
 1997 0.7545345 
 1998 0.7515149 
 1999 0.7777944 
 2000 0.872868 
 2001 0.9586731 
 2002 0.9570606 
 2003 0.9061076 
 2004 0.9279277 
 2005 0.9950102