Year	Number
1967	-5
1968	-5
1969	-5
1970	-6
1971	-6
1972	-6
1973	-6
1974	-7
1975	-7
1976	-7
1977	-7
1978	-8
1979	-8
1980	-8
1981	-8
1982	-8
1983	-8
1984	-8
1985	-8
1986	-7
1987	-7
1988	-7
1989	-7
1990	-7