# year    value 
 1980 -0.03723442 
 1981 0.04683753 
 1982 -0.2832395 
 1983 -0.3075193 
 1984 -0.1642056 
 1985 -0.03769947 
 1986 0.02925587 
 1987 0.1305452 
 1988 0.1691437 
 1989 0.2251772 
 1990 0.1669994 
 1991 -0.03892286 
 1992 -0.2212723 
 1993 0.009155591 
 1994 0.1604931 
 1995 0.1450291 
 1996 0.3307067 
 1997 0.2761576 
 1998 0.4193138 
 1999 0.4523845 
 2000 0.4666182 
 2001 0.6446819 
 2002 0.5660317 
 2003 0.576627 
 2004 0.6196644 
 2005 0.6927826