# year    value 
 1980 -0.005177625 
 1981 0.02477146 
 1982 -0.1794701 
 1983 -0.2794791 
 1984 -0.144165 
 1985 -0.05892948 
 1986 -0.02123003 
 1987 0.08830583 
 1988 0.1934104 
 1989 0.2012999 
 1990 0.2424345 
 1991 0.04085604 
 1992 -0.2028894 
 1993 -0.01124241 
 1994 0.1371314 
 1995 0.2171964 
 1996 0.2928767 
 1997 0.3638205 
 1998 0.4735756 
 1999 0.4574862 
 2000 0.568127 
 2001 0.6348191 
 2002 0.6480066 
 2003 0.6450397 
 2004 0.6415975 
 2005 0.7090813