Year	Number
1960	35
1961	32
1962	29
1963	26
1964	23
1965	21
1966	19
1967	18
1968	18
1969	18
1970	18
1971	17
1972	16
1973	15
1974	14
1975	14
1976	13
1977	13
1978	14
1979	14
1980	14
1981	15
1982	15
1983	16
1984	16
1985	16
1986	16
1987	16
1988	16
1989	16
1990	16
1991	16
1992	16
1993	16
1994	15
1995	14
1996	14
1997	13
1998	12
1999	12
2000	11
2001	10
2002	10
2003	9
2004	9
2005	9
2006	8
2007	8
2008	8
2009	7
2010	7
2011	7
2012	7
2013	7
2014	7
2015	6
2016	6
2017	6
2018	6
2019	6
2020	6
2021	5
2022	5