Year	Number
1962	8
1963	8
1964	8
1965	8
1966	8
1967	8
1968	8
1969	8
1970	8
1971	8
1972	8
1973	8
1974	8
1975	8
1976	8
1977	8
1978	8
1979	8
1980	8
1981	8
1982	8
1983	8
1984	9
1985	9
1986	9
1987	9
1988	9
1989	9
1990	9
1991	9
1992	9
1993	9
1994	9
1995	9
1996	9
1997	10
1998	10
1999	10
2000	10
2001	10
2002	10
2003	10
2004	10
2005	10
2006	10
2007	10
2008	10
2009	10
2010	10
2011	10