1981 -2.8 1982 -3.1 1983 -2.4 1984 -4.0 1985 -3.7 1986 -4.9 1987 -3.4 1988 -3.8 1989 -1.2 1990 -2.1 1991 -0.7 1992 -1.9 1993 -1.2 1994 -2.0 1995 -2.3 1996 -2.4 1997 -1.7 1998 -3.0 1999 -2.8 2000 -2.7 2001 -4.6 2002 -2.2 2003 -3.4 2004 -1.3 2005 -2.7 2006 -3.1 2007 -1.3 2008 -2.8 2009 -0.9 2010 -2.0