Year	Number
1957	10
1958	10
1959	10
1960	10
1961	10
1962	10
1963	10
1964	10
1965	10
1966	10
1967	10
1968	10
1969	1
1970	1
1971	4
1972	4
1973	4
1974	4
1975	4
1976	4
1977	4
1978	4
1979	4
1980	4
1981	4
1982	4
1983	4
1984	4
1985	4
1986	4
1987	4
1988	4
1989	4
1990	4
1991	4
1992	4
1993	4
1994	4
1995	3
1996	3
1997	3
1998	3
1999	3
2000	3
2001	3
2002	3
2003	3
2004	3
2005	3
2006	3
2007	3
2008	6
2009	6
2010	6
2011	6