1971 -3.6 1972 -3.0 1973 -1.7 1974 -2.8 1975 -4.2 1976 -3.3 1977 -5.0 1978 -4.5 1979 -3.0 1980 -2.9 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