1976 91 16.7 1977 105 17.1 1978 106 18.2 1979 108 18.1 1980 88 17.2 1981 91 18.2 1982 58 16 1983 82 17.2 1984 81 18 1985 65 17.2 1986 61 16.9 1987 48 17.1 1988 61 18.2 1989 43 17.3 1990 33 17.5 1991 36 16.6