# year    value 
 1980 0.6577249 
 1981 0.6741321 
 1982 0.5774485 
 1983 0.3661633 
 1984 0.4936807 
 1985 0.5676571 
 1986 0.5282329 
 1987 0.5975004 
 1988 0.7639935 
 1989 0.7484133 
 1990 0.7927823 
 1991 0.8203833 
 1992 0.3188353 
 1993 0.5206713 
 1994 0.6232579 
 1995 0.6671946 
 1996 0.7812442 
 1997 0.8518862 
 1998 0.9295912 
 1999 0.9513227 
 2000 0.951717 
 2001 1.003755 
 2002 1.122643 
 2003 1.076516 
 2004  1.09838 
 2005  1.10514