Year	Number
1970	8565
1971	6907
1972	6072
1973	5882
1974	5400
1975	5960
1976	7898
1977	12192
1978	14143
1979	16784
1980	12410
1981	14532
1982	0
1984	0
1985	0
1986	0
1988	0
1989	0
1990	0
1991	0
1993	0
1994	0
1995	0
2001	0
2003	1893
2004	2765
2005	9011
2007	7400
2008	9716
2009	22711
2011	18085
2012	23419
2013	29520
2014	25019
2015	26986
2016	25629
2017	23766
2018	21902