Year	Number
1961	40
1962	40
1963	40
1964	40
1965	45
1966	50
1967	52
1968	52
1969	52
1970	52
1971	50
1972	50
1973	45
1974	40
1975	36
1976	34
1977	35
1978	36
1979	37
1980	40
1981	40
1982	40
1983	40
1984	40
1985	40
1986	44
1987	48
1988	48
1989	47
1990	47
1991	48
1992	48
1993	48
1994	45
1995	45
1996	45
1997	45
1998	45