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