Year	Percent
1965	6
1966	6
1967	7
1968	7
1969	6
1970	6
1971	6
1972	6
1973	6
1974	6
1975	6
1976	6
1977	8
1978	8
1979	10
1980	12
1981	12
1982	12
1983	14
1984	14
1985	14
1986	16
1987	16
1988	16
1989	16
1990	55
1991	55