Year	Number
1961	5
1962	5
1963	5
1964	5
1965	5
1966	5
1967	5
1968	6
1969	8
1970	10
1971	12
1972	13
1973	20
1974	27
1975	34
1976	40
1977	48
1978	55
1979	62
1980	72
1981	72
1982	72
1983	72