# year    value 
 1980 -0.4128779 
 1981 -0.3642902 
 1982 -0.5700378 
 1983 -0.5684541 
 1984 -0.5109832 
 1985 -0.4584798 
 1986 -0.319139 
 1987 -0.2366504 
 1988 -0.2889293 
 1989 -0.09005215 
 1990 -0.1883936 
 1991 -0.397395 
 1992 -0.5793173 
 1993 -0.3758596 
 1994 -0.2166497 
 1995 -0.183437 
 1996 0.03162709 
 1997 -0.03414802 
 1998 0.05262773 
 1999 0.04800038 
 2000 0.1499552 
 2001 0.2552915 
 2002 0.1449932 
 2003 0.2372699 
 2004 0.2023061 
 2005 0.3105794