Year	Number
1960	24
1961	22
1962	20
1963	18
1964	17
1965	15
1966	14
1967	13
1968	12
1969	12
1970	11
1971	10
1972	10
1973	10
1974	10
1975	10
1976	10
1977	10
1978	10
1979	10
1980	9
1981	9
1982	8
1983	8
1984	7
1985	7
1986	6
1987	6
1988	6
1989	5
1990	5
1991	5
1992	5
1993	5
1994	5
1995	5
1996	5
1997	5
1998	5
1999	4
2000	5
2001	4
2002	4
2003	4
2004	4
2005	4
2006	4
2007	4
2008	4
2009	4
2010	4
2011	4
2012	4
2013	4
2014	4
2015	4
2016	4
2017	3
2018	3
2019	3
2020	3
2021	3
2022	3