# year    value 
 1980 -0.3004419 
 1981 -0.2425664 
 1982 -0.3865002 
 1983 -0.5756472 
 1984 -0.4022579 
 1985 -0.3643534 
 1986 -0.3149656 
 1987 -0.2399402 
 1988 -0.1298027 
 1989 -0.1036855 
 1990 -0.05014759 
 1991 -0.1297191 
 1992 -0.4757653 
 1993 -0.3538142 
 1994 -0.2199662 
 1995 -0.1419005 
 1996 -0.02734016 
 1997 0.04699113 
 1998 0.1164385 
 1999 0.09851211 
 2000 0.2171249 
 2001 0.3029367 
 2002 0.3069401 
 2003 0.3330348 
 2004 0.339415 
 2005 1.163071