Year	Number of
1952	47
1953	47
1954	47
1955	48
1956	50
1957	51
1958	53
1959	54
1960	55
1961	56
1962	55
1963	54
1964	52
1965	50
1966	48
1967	46
1968	43
1969	41
1970	39
1971	38
1972	38
1973	37
1974	36
1975	33
1976	31
1977	28
1978	26
1979	24
1980	22
1981	21
1982	20
1983	20
1984	19
1985	19
1986	18
1987	17
1988	16
1989	15
1990	15
1991	15
1992	14
1993	14
1994	13
1995	13
1996	12
1997	11
1998	10
1999	9
2000	8
2001	8
2002	7
2003	7
2004	7
2005	7
2006	6
2007	6
2008	6
2009	6
2010	6
2011	5
2012	5
2013	5
2014	4
2015	4