# year    value 
 1980 0.519527 
 1981 0.4773463 
 1982 0.4290194 
 1983 0.3112368 
 1984 0.3861536 
 1985 0.4167461 
 1986 0.5119675 
 1987 0.5656531 
 1988 0.5644229 
 1989 0.6014664 
 1990 0.6392207 
 1991 0.6761556 
 1992 0.3758262 
 1993 0.4383252 
 1994 0.4575045 
 1995 0.4421206 
 1996 0.5721285 
 1997 0.6766381 
 1998 0.7402596 
 1999 0.7352322 
 2000 0.7236794 
 2001 0.8458745 
 2002 0.9367377 
 2003 0.8224914 
 2004 0.7844325 
 2005 0.862174