Year	Number
1961	3
1962	3
1963	5
1964	5
1965	6
1966	10
1967	10
1968	12
1969	12
1970	12
1971	12
1972	12
1973	12
1974	12
1975	12
1976	12
1977	12
1978	12
1979	12
1980	12
1981	11
1982	11
1983	11
1984	11
1985	11
1986	11
1987	11
1988	11
1989	11
1990	11
1991	11
1992	11
1993	11
1994	11
1995	11
1996	11
1997	11
1998	11
1999	11
2000	17
2002	30
2003	36