# year    value 
 1980 0.02317179 
 1981 0.04473823 
 1982 -0.04260839 
 1983 -0.244884 
 1984 -0.07928593 
 1985 -0.04852897 
 1986 -0.1044111 
 1987 -0.01162035 
 1988 0.1373657 
 1989 0.1045311 
 1990 0.178644 
 1991 0.1847976 
 1992 -0.2260577 
 1993 -0.003103803 
 1994 -0.0175719 
 1995 0.00193123 
 1996 0.1582181 
 1997 0.2186051 
 1998 0.242115 
 1999 0.293698 
 2000 0.254547 
 2001 0.3847361 
 2002 0.4994726 
 2003 0.3382937 
 2004 0.3646204 
 2005 0.4771066