Year	Number of
1970	87
1971	80
1972	76
1973	74
1974	72
1975	70
1976	67
1977	65
1978	62
1979	59
1980	56
1981	52
1982	49
1983	45
1984	41
1985	38
1986	35
1987	32
1988	29
1989	27
1990	26
1991	24
1992	23
1993	23
1994	22
1995	22
1996	21
1997	21
1998	20
1999	19
2000	19
2001	18
2002	16
2003	15
2004	14
2005	14
2006	13
2007	13
2008	13
2009	13
2010	12
2011	12
2012	11
2013	11
2014	10
2015	10