Year	Number
1971	3555
1972	4084
1973	4580
1974	5053
1975	5729
1976	6360
1977	7269
1978	7920
1979	7947
1980	7722
1981	8035
1982	8385
1983	8346
1984	8968
1985	9448
1986	9623
1987	9690
1988	10099
1989	10288
1990	10310
1991	7034
1992	6967
1993	7526
1994	8229
1995	9021
1996	9747
1997	10180
1998	10798
1999	10389
2000	10176
2001	10489
2002	10940
2003	11594
2004	12321
2005	16815
2006	20056
2007	22016
2008	22895
2009	24605
2010	25520
2011	25983
2012	26775
2013	27801
2014	28610
2015	29810
2016	30635
2017	31081
2018	31524
2019	33015
2020	34105
2021	32782