Year	Number
1971	3969
1972	4102
1973	3744
1974	4517
1975	6295
1976	7143
1977	6663
1978	7398
1979	7872
1980	7967
1981	8899
1982	10509
1983	8971
1984	9616
1985	11390
1986	13037
1987	16798
1988	18108
1989	22225
1990	23023
1991	36773
1992	40334
1993	46381
1995	47636
2000	105473
2001	104885
2002	113176
2003	119077
2004	140735
2005	159240
2006	180384
2007	197315
2008	230572
2009	275160
2010	322112
2011	362111
2012	402733
2013	464709
2014	546282
2015	615946
2016	672472
2017	598006
2018	606024