Year	Number
1970	65783
1971	46213
1972	40485
1973	35749
1975	32383
1976	34001
1978	28884
1979	33924
1980	37880
1981	42838
1982	46632
1983	50940
1984	52139
1985	50528
1986	50956
1987	48600
1988	51768
1989	47024
1990	46647
1999	25845
2000	19390
2001	14643
2002	6513
2004	5561
2005	7355
2006	5007
2007	5410
2008	9981
2009	22698
2010	15886
2011	20766
2012	22691
2013	30229
2014	41136
2015	53667